Steam generation with coal

ABSTRACT

Heat is generated by combustion of coal or like carbonaceous fuel reactant dissolved in molten salt. The generated heat is transferred to steam by an alternating sequence of direct contact heat exchanges of the salt and steam with a common heat transfer medium.

This is a division of application Ser. No. 512,540 now U.S. Pat. No.3,933,128 filed 10/7/74.

BACKGROUND

This invention has to do with process and apparatus for the generationand recovery of heat from highly aromatic, generally refractorycarbonaceous fuel reactants, particularly from coals and residual oils.Such fuel reactants may be "char" derived from pyrolysis or otherrigorous treatment of bituminous, or sub-bituminous coals or heavy crudeoil residue feedstocks, or be anthractie coals or like materialstypically characterized by being predominantly carbon i.e. carbonaceousand predominantly aromatic rather than aliphatic in their carbonstructure and generally refractory i.e. highly resistant to thermaldecomposition.

More particularly, the invention relates to process and apparatus highlyadvantageous for obtaining maximum heat from such fuel reactants forproduction of steam useful e.g. for power turbines, while simultaneouslyprecluding the release of atmospheric contaminants, particularly NO_(x),and reducing the size and complexity of capital equipment relative toconventional heat and steam generation facilities, and with minimum heatloss through the process steps. In general, the process involvessignificant breakthroughs in the generation of heat from the mentionedfuel reactants and numerous innovations in the handling of such heat formaximum benefit at minimum cost.

At the outset it must be mentioned that the process overall is readilyconducted at relatively low temperatures i.e. less than 1000° C.,temperatures below those at which significant formation of nitrogenoxides takes place. Thus the process achieves the long sought goal ofefficient conversion of e.g. coal to heat, without concomitantatmospheric contamination. In particular embodiments the use of nitrogencontaining gases such as air is avoided, by the use, instead, of solidoxidizers such as metal bearing ores, but in all embodiments lowreaction temperatures, possible through catalytic action and solutionreaction occurring in the process, enable efficient combustion of fuelreactant without substantial co-production of NO_(x).

PRIOR ART

The need to obtain fully from coal and oil residues the latent heatenergy and/or chemicals content has been long manifest, buttechnological and economic difficulties have together or separatelyheretofore limited heat and chemical production from coal and oilresidues except in a few well-trodden areas. The science of coalcombustion for maximum heat has been well developed, but is currentlyundergoing revision as stringent air and water pollution standards aresettled upon municipalities and industrial users. So at a time when thecountry's most abundant natural fuel resource is most needed, to provideboth chemicals and heat energy, owing to the vagaries of theinternational oil market, the contamination factors inherent in coalconsumption i.e. sulfur oxides and nitrogen oxides emitted into theatmosphere are increasingly less tolerated, posing the dilemma ofgreater need and less legal ability to derive more heat and energy andchemicals from coal. Similarly, it is now highly important to make thebest and highest economic use of all fractions of crude oil meaning thatthe carbonaceous residues from which all possible chemicals have beenobtained by earlier processing must be converted as much as possible tousable heat, also without lessening air quality.

In general, previous efforts at meeting these needs have been directedat improvements in reaction rate e.g. through catalysis, downstreammodification of exhaust gases to remove contaminants and other ratherspecific additives to the overall process which have predictablyproduced only rather specific narrow benefits. In the matter of heattransfer from the reaction mass to steam e.g. for turbines, conventionalheat exchange approaches remain with all the inherent inefficiencies andtemperature limitations of limited surface heat transfer through fixedsurface heat exchangers.

The United States is thereby being deprived of full use of its mostsignificant fuel resource: Coal. Power plants in particular haveskyrocketed in cost and complexity as utilities have been forced to addpollution control equipment which rivals in cost the power plant itself.More advanced technology such as nuclear energy has its own critics andis fraught with administrative and environmental delays.

It is into this area that the present invention takes a significantstep. The present process and apparatus through adaptations of solutionand catalytic reactions, in a recyclable salt matrix, effect heatproduction at super-rapid rates and transfer this heat with greatrapidity and efficiency through a dispersible and reformable heattransfer fluid in direct contact with the salt matrix on the one handand the steam for power generation on the other hand, and alternately.The rate of combustion of the coal or like residual feedstock is sorapid that capital equipment is able to be reduced in size and coststhereof are commensurately reduced. Moreover the temperatures ofcombustion are not favorable to NO_(x) formation and solid contaminantssuch as sulfur and ash are retained wtihin the salt matrix and notvented to the atmosphere, but are removed at a selected controllablepoint in the process cycle for minimum contamination and maximumproductivity.

SUMMARY

It is an object therefore of the present invention to provide processand apparatus in which reaction conditions and heat handling stages arecomplementary and integrated for maximum efficiency in combustion andheat transfer. Other objects include conducting the combustion reactionat temperatures and under conditions:

a. limiting generation of NO_(x),

b. providing readily separable ash and other by-products,

c. capturing heat directly during combustion in the reaction medium,

d. effecting heat transfer directly from the reaction medium to a heattransfer medium in intimate contact therewith,

e. effecting a further transfer of heat from the heat transfer medium tosteam directly and out of contact with the reaction medium,

f. protecting the rection apparatus from undue heat emanations from thereactor while preheating reactants and/or steam; and

g. in certain embodiments simultaneously reducing a metal bearing orewhile oxidizing the fuel reactant; and

h. differentially passing streams of reactants, products and the heattransfer medium to define reaction times and maximize heat transfer, andutilizing heat energies of exhaust gases in effecting the process.

Other objects will be evident from the following description of processsteps and apparatus.

GENERAL SUMMARY OF THE PROCESS

In accordance with the invention the foregoing and the other objects ofthe invention are realized in the process for the generation andrecovery of heat from highly aromatic, refractory carbonaceous fuelreactants by oxidizing the fuel in a molten salt matrix within areaction zone and recovering heat of combustion from the salt matrix,which includes the step of dissolving the fuel in the salt in advance offuel oxidation. The salt solution typically comprises from 2 to 10% byweight of the fuel reactant and has a temperature during oxidationbetween 600° C. and 1000° C. The fuel reactant may comprise coal orother feedstock substantially free of volatiles at 600° C. and 10atmospheres.

ORE REDUCTION -- COMBUSTION

In one embodiment, there is contemplated adding a metal oxide to thesalt-fuel reactant solution to effect the oxidation while effectivelysimultaneously reducing the oxide to free metal. The metal oxide ispreferably selected from among naturally occurring metal oxides ofmetals of Group VII of the Periodic Table and particularly iron ore ornickel ore and the process thus contemplates obtaining free iron and/ornickel from the salt solution.

OXIDIZING GAS COMBUSTION

In other embodiments an oxidizing gas is passed through the saltsolution to effect the oxidation. Such gas is typically freeoxygen-containing and may be oxygen per se, oxygen enriched air, or air.In these embodiments, the oxidizing gas is generally treated bypreheating and precompressing in advance of passage through the saltsolution. For this purpose using exhaust gases e.g. by expanding andcooling these exhaust gases through an expansion motor, and compressingthe oxidizing gas with the mechanical energy derived from the expansion.Additionally, there may be mentioned heat exchanging the hot combustiongases with the compressed oxidizing gas being passed to the salt-fuelsolution, in advance of expanding and cooling the hot combustion gases;and further the expanded and cooled combustion gases may be first heatexchanged with the compressed oxidizing gas in advance of heat exchangeswith the hot combustion gases.

MOLTEN SALT RECYCLE

The process further includes recycling the molten salt solvent andreaction matrix for the fuel reactant to and from the reaction zone,removing heat from the salt outside the reaction zone, and alsorecharging the molten salt with fresh fuel reactant outside the reactionzone.

Where the fuel reactant is sub-anthracite coal e.g. bituminous,sub-bituminous or lignite orders of coal, the invention process mayfurther include pretreating the fuel reactant in the molten salt inadvance of the reaction zone to substantially free the reactant ofcomponents volatile at 400° C. and 10 atmospheres.

HEAT TRANSFER

Heat transfer according to the invention may be effected by heatexchanging the salt outside the reaction zone with a high specific heatfluid which may be passed in e.g. indirect heat exchange relation overthe exterior surfaces of the reaction zone to absorb emanated heat andprotect the reaction zone support structure. The high specific heatfluid typically is liquid, immiscible with the molten salt and of adifferent density therefrom, the process including direct contact heatexchanging the salt and this liquid. The liquid may be metallic and theprocess then includes passing the salt and metallic liquid in contacttherewith through a heat exchange zone. For example, the processincludes in preferred embodiments passing the salt and metallic liquidcountercurrently along an extended heat exchange path and differentiallyat opposite ends of the path to maintain relatively longer contact ofmetallic liquid with the salt at maximum temperature and relativelyshorter contact thereof with minimum temperature salt along the path. Inparticular embodiments, the metallic liquid is dispersed throughout thissalt in a multiplicity of different mass droplets, and the processprovides for subjecting the droplets to opposing forces along the path,one of which forces is directly proportional to the specific mass of thedroplets, and segregating the droplets by their specific mass forseparation selectively of the greater mass droplets. The droplets may besubjected to gravity as the one force and entrainment in the saltflowing countercurrently along the droplet path as the other path, andaggregating and coalescing the droplets to a mass sufficient to overcomethe entraining force of the moving salt, for segregation and separation.The gravity force and the entraining force may be approximately balancedalong the droplet path at the reaction zone region of maximum salttemperature to maximize metallic liquid dwell times and thus heattransfer from the salt to the metallic liquid in this region.

In other embodiments the droplets may be subjected to centrifugal forceas the one force and entrainment in the salt flowing countercurrentlyalong the droplet path again as the other force and the process thenincludes aggregating and coalescing the droplets to a mass sufficient toovercome the entraining force of the moving salt, for segregation andseparation. As in the gravity embodiment, the two forces, centrifugalforce and entraining force, may be approximately balanced along thedroplet path at the region of maximum salt temperature to maximizemetallic liquid dwell times and thus heat transfer from the salt to themetallic liquid in this region.

STEAM

The high specific heat fluid being typically nonaqueous, the processincludes following heat transfer thereto from the salt, subsequentlyheat exchanging the high specific heat fluid with steam to transfer themolten salt heat to the steam through the high specific heat fluid as aspecific instance of direct contact heat exchanging a salt immiscibleliquid with steam to transfer the molten salt heat to the steam throughthe immiscible liquid. In preferred embodiments the immiscible highspecific heat liquid is the mentioned metallic liquid and the processfurther includes circulating the metal liquid through the salt in directcontact heat exchange relation and in sequence through steam, andreturning the metallic liquid to the salt for continuing heat transferfrom the salt to the steam thereby.

In an integrated form of the process then, the molten salt is circulatedto and from the reaction zone to bring fresh charges of fuel reactantinto the zone and heat out of the zone in a reaction stream loop, andthe metallic liquid is circulated sequentially through the circulatingsalt in differential flow relation and through steam and back to thesalt in a heat transfer loop, and, thus-heated steam is circulated to asteam energy consuming zone and back in a steam loop to the heattransfer loop for regeneration.

The process includes use of lead or the metallic liquid, and alsoultimately dispersing the lead into droplets in the salt for receptionof heat and coalescing for separation from the salt. Accordingly whenusing lead heat transfer medium, the invention includes maintaining thedifferential flow of salt and the lead droplets therein by balancingforces acting on the lead in a manner relatively increasing the leadexposure to maximum temperature salt and relatively decreasing the leadexposure to minimum temperature salt and responsive to the mass of thedroplets so that upon coalescense of the droplets they are separablefrom the salt.

REACTION ZONES

The liquid lead may be passed over the exterior surfaces of the reactionzone to retain heat normally emanated from the reaction zone in theprocess. In such embodiment, the process may further include passing afree oxygen containing gas in indirect heat exchange with the liquidlead at the exterior surface of the reaction zone, and the passing ofthe gas thus preheated into the reaction zone to oxidize the fuelreactant therein.

The reaction zone is typically vertically extended in one embodiment,and the process then includes within the reaction zone raining moltensalt-fuel reactant solution in droplet form through an updraft of air asthe oxidizing gas, and collecting molten salt containing the heat ofcombustion at the lower reaches of the reaction zone. In such a zone theprocess further includes balancing the gravitational forces acting onthe falling molten-salt-fuel reactant solution droplets with the forceof air to suspend temporarily the droplets above the lower reaches ofthe reaction zone for a time to substantially free the salt of fuelreactant.

In alternative reaction zone design embodiments, the reaction zone maybe discoid and the process then includes introducing the moltensalt-fuel reactant centrally thereof for outward passage through thereaction zone in droplet form, introducing air tangentially at theperiphery of the reaction zone along a spiral path extending toward thecenter of the zone in a manner entraining the salt solution-fuelreactant droplets for passage toward the center of the zone, andsimultaneously subjecting the droplets to centrifugal forces opposingsuch passage, and collecting molten salt containing heat of combustionat the peripheral reaches of the reaction zone. It is furthercontemplated to balance the centrifugal forces acting on the moltensalt-fuel reactant solution droplets with the force of air to suspendtemporarily the droplets inwardly of the reaction zone periphery for atime to substantially free the salt of fuel reactant.

PREFERRED PROCESS SUMMARY

In summary of one of the preferred embodiments of the process the fuelreactant dissolved in the salt is oxidized with free oxygen-containinggas in a vertically extended reaction zone, the process including withinthe reaction zone raining molten salt-fuel reactant solution in dropletform through an updraft of the gas, and collecting molten saltcontaining the heat of combustion at the lower reaches of the zone, thegas updraft balancing with the force of the gas the gravitational forcesacting on the falling molten salt-fuel solution droplets to suspendtemporarily the droplets above the lower reaches of the reaction zonefor a time sufficient to substantially free the salt of fuel reactant,e.g. 0.2 to 2 seconds.

In summary of another of the preferred embodiments of the process, thefuel reactant is oxidized with a free oxygen-containing gas in a discoidreaction zone and the process includes introducing the molten salt-fuelreactant centrally thereof for outward passage through the reaction zonein droplet form, introducing the gas tangentially at the periphery ofthe zone along a spiral path extending toward the center of the zone ina manner entraining the salt solution fuel reactant droplets for passagetoward the center of the zone, and simultaneously subjecting thedroplets to centrifugal forces opposing such passage, and collectingmolten salt containing heat of combustion at the peripheral reaches ofthe reaction zone, thus the force of the gas balancing the centrifugalforces acting on the molten salt-fuel reactant solution droplets tosuspend temporarily the droplets for a time sufficient to substantiallyfree the salt of fuel reactant e.g. 0.2 to 2 seconds.

INTEGRATED OPERATIONS SUMMARY

In summary then, the process of the invention includes forming asolution in molten salt of from 2 to 10% by weight of highly aromatic,refractory fuel reactant, passing the salt-fuel reactant solution indispersed form through a counter-flowing free-oxygen containing gasstream in a reaction zone at a temperature between 600° C. and 1000° C.and a pressure between about 1 and 25 atmospheres, and at a differentialrate decreased in proportion to relatively greater amount of fuelreactant in the salt to be combusted and for a time sufficient tocombust substantially all of the fuel reactant from the salt, recoveringa major portion of the heat produced by fuel reactant combustion in thesalt, collecting the salt and transferring heat from the salt to liquidmetal heat transfer medium in direct contact therewith outside thereaction zone, retransferring the heat from the heat transfer medium bydirect contact to steam for consumer operations, recirculating themolten salt with a fresh charge of fuel reactant to the reaction zone,recirculating the liquid metal heat transfer medium between directcontact alternately with said salt and said steam, and purging mineralwastes and atmospheric contaminants from the recirculating salt. Theprocess thus defined may further include dispersing the salt-fuelreactant solution as droplets in the gas, and simultaneously subjectingthe solution droplets to countervailing forces in relatively balancedrelation to provide time for substantially complete combustion of thefuel reactant in the reaction zone e.g. a dwell time for the saltsolution of the reactant of between 0.2 and 2 seconds. Thus when thereaction zone is vertically extended, the countervailing force to thegas is gravitational by virtue of the introduction of the droplets atthe top of the reaction zone to fall to the bottom thereof. And when thereaction zone is discoid, the countervailing force is centrifugal fromthe introduction of the droplets at the center of the zone and theentrainment of the droplets in spirally moving gas passing from theperiphery toward the center of the zone. For this purpose the processincludes jetting the salt-fuel reactant in angularly colliding streamswithin the reaction zone to fan the solution and form the dropletsthereby. Additionally in this embodiment, the gas and solution dropletsmay travel spiral paths of different pitch, the spiral path of thedroplets being greater and being the vector sum of the dropletentraining force and centrifugal force components.

APPARATUS ASPECTS

Apparatus is provided for carrying out the foregoing process inaccordance with the present invention. Apparatus therefore is providedfor the generation and recovery of heat from highly aromatic, refractorycarbonaceous fuel reactants, the fuel reactants being predissolved in amolten salt solvent therefor, the apparatus comprising a reactordefining a through passage for the salt solution of fuel reactant, meansto pass a free oxygen-containing gas through the reactor differentiallyto the salt fuel reactant solution in combustion heat-absorbingrelation, and means beyond the reactor to transfer the heat from thesalt, including a high specific heat fluid, and means to recharge themolten salt with fresh fuel reactant following heat transfer and toreturn the recharged salt to the reactor. The apparatus may also includemeans to pass the high specific heat fluid across the external surfaceof the reactor to absorb heat emanated therefrom, and means to pass theoxygen-containing gas in indirect heat transfer relation with fluid, topreheat the gas for the reactor.

VERTICAL REACTOR

In particular embodiments the reactor may be generally cylindrical, andinclude a first external jacket enclosing the reactor and a secondexternal jacket enclosing the first jacket; the first jacket defining aflow passage for the heat transfer fluid; and the second jacketcommunicating with the reactor interior and defining a flow passage forthe gas to the reactor interior. The reactor thus described mayterminate in a salt receiving receptacle having a salt outlet oppositethe salt fuel solution inlet and further including gas inlets adjacentlyinward of the receptacle. The invention further contemplates the reactorapparatus including means to disperse the salt fuel solution intodroplets moving differentially past the gas within the reactor. Thereactor may be extended and the salt fuel solution introduced at oneterminus of the reactor, the apparatus then including means introducingthe gas through an inlet at the opposed terminus of the reactor.Accordingly the reactor may be vertically extended and the salt fuelsolution droplet-dispensing inlet may be located at the upper end of thereactor and the apparatus also include means to pass gas upward throughthe reactor at a rate suspending the droplets in dynamic equilibrium ina zone adjacent to the gas inlet to the reactor.

In the foregoing and other embodiments of the invention the gasintroduced into the reactor may be preheated indirectly by heat ofcombustion in advance of its introduction into the reactor. Accordinglyheat transfer fluid may be passed between the reactor and the gas as anindirect heat transfer medium by appropriate means such as a jacketenclosing the reactor.

DISCOID REACTION

In alternative embodiments the reactor is discoid in configuration andthe salt-fuel solution droplet dispensing inlet is located at thecentral portion of the reactor and the apparatus further includes meansto pass the gas inward through said reactor at a rate and in a directionsuspending the droplets in dynamic equilibrium in an anular zoneadjacent the gas inlet to the reactor. For this purpose the discoidreactor may further include at its periphery a tangentially oriented gasinlet means and a gas outlet means at the central portion thereof, eacharranged to pass gas along a spiral path inwardly through the reactor.Accordingly the discoid apparatus embodiment may include opposed upperand lower salt-fuel solution inlet nozzles annularly related tointersect streams of the solution for dispersion thereof in droplet formwithin the reactor. Upper and lower plenums may be providedcommunicating with the solution inlet nozzles for the purpose ofsupplying fuel-salt solution thereto. There may be further provided saltcollector means located peripherally of the reactor in receivingrelation to salt passing through the gas. Additionally there may beprovided means to preheat gas to be introduced into the discoid reactorwith heat emanated from the reactor. Typically the reactor includesexternal support structure and the invention contemplates providing alsomeans to pass heat transfer fluid across the reactor external surface toabsorb heat emanated from the reactor to protect the external supportstructure, the apparatus further including means to transfer heatindirectly from the heat transfer fluid to the gas to be introduced intothe reactor, to preheat the gas.

In specific embodiments then, the apparatus includes a first jacketgenerally enclosing the discoid reactor, a second jacket generallyenclosing the first jacket, the first jacket defining a passage for theheat transfer fluid in heat transfer relation with the reactor; thesecond jacket defining a through passage in heat transfer relation tothe first passage for gas to be introduced into the reactor; andadditionally a gas inlet port communicating the gas passage jacket withthe reactor interior in fluid free relation through the first jacket andradially inward of the salt collector.

EXHAUST GAS UTILIZATION

The invention contemplates utilization of exhaust gases from the reactorcombustion and for this purpose the apparatus includes means to pass theexhaust gases from the reactor, means to expand and do work with theexhaust gases including compression and heating of free oxygencontaining gas to be introduced into the reactor. For this purpose theremay be provided a turbo-expander and compressor and means to passexhaust gases through the expander and means to pass free oxygencontaining gas through the compressor, the expander being operativelycoupled to the compressor to compress the free oxygen containing gaswith the expansion energy of the exhaust gases. The invention furthercontemplates means to heat exchange the exhaust gases before and aftertheir expansion with compressed free oxygen containing gas.

SEPARATION OF SOLID CONTAMINANTS

An important aspect of the present apparatus is provision of means forthe removal of solid contaminants including particularly fly ash andother mineral matter such as separable sulfur compounds. For thispurpose the invention provides means to separate insoluble mineralmatter left in the salt from the reaction, from the salt, including agenerally cylindrical settling chamber having a tangential inlet for thesalt and mineral matter mixed therewith, and an axial outlet for thesalt above the bottom of the chamber, means to introduce the mixture ata rate imparting a circular flow of the mixture and a centrifugal forcedriving the mineral matter preferentially to the chamber perimeter, andmeans to draw off the mineral matter at the chamber perimeter. Infurther detail the mineral matter separation device may include apositive displacement means communicating with the chamber perimeter andadapted to receive and remove mineral matter there. The positivedisplacement means may comprise a rotating screw.

DIRECT CONTACT HEAT EXCHANGERS

A further important aspect of the present invention is the provision ofhighly efficient heat transfer through direct contact heat exchanges ofan innovative design. For this purpose the invention provides a heattransfer means comprising a heat exchanger and further including meansto pass a high specific heat fluid through the heat exchanger with thesalt obtained from the reactor, and in heat transferring relation. Forthis purpose the invention provides means to recirculate molten saltfrom the reactor to the heat exchanger. The high specific heat fluid maycomprise metallic liquid and the apparatus may include means to pass theliquid into and out of exchange contact with the salt in the heatexchanger and additionally second heat exchange means to transfer heatfrom the metallic liquid to steam. Accordingly the invention providesloop means including the first and second heat exchangers and adapted torecirculate the metalic liquid between the heat exchangers. The firstheat exchanger may be a direct contact heat exchanger and the secondheat exchanger may also be a direct contact heat exchanger. In theseembodiments the first heat exchanger comprises an extended exchangechamber and means to pass the salt and the metallic liquid heat transferfluid differentially through the exchange chamber. Such first heatexchanger comprises a vertically elongated exchange chamber having ametallic liquid inlet at the upper portion thereof and a metallic liquidoutlet at the lower portion thereof, the salt chamber further having asalt inlet at the lower portion thereof and a salt outlet at the upperportion thereof for passage of salt upwardly through the chamber, andmeans at the metallic liquid inlet to disperse the liquid into andthrough the upward moving salt and at the liquid outlet to recover saidliquid, coalesced, and containing the transferred heat of the salt. Inpreferred embodiments the metallic liquid is molten lead.

The second heat exchanger comprises means to intimately interdispersethe metallic liquid and steam to transfer the salt heat contained insaid metallic liquid thereby to the steam. The second heat exchangerfurther comprises means to intimately interdisperse the molten lead andsteam, to thereby transfer the salt heat contained in the lead to thesteam. The apparatus then further includes a steam turbine adapted toreceive steam from a second heat exchanger, and means to recycle steamfrom the steam turbine to the second heat exchanger for reheating in asteam loop.

In particular embodiments provision is made for protecting the externalsupport structure of the first heat exchanger including means to passrelatively cooler heat transfering metallic liquid over the externalsurface of the first heat exchanger to absorb heat emanated from theheat exchanger to protect the external support structure. For thispurpose there may be provided a first jacket generally enclosing thefirst heat exchange means the jacket defining a flow passage for themetallic liquid. Further, means may be provided to pass processed steamin heat transfering relation across the external surface of the firstheat exchanger. Therefore there may be provided a second jacketgenerally enclosing the first jacket and defining dimension to passagefor process steam in heat transfer relation with metallic liquid in thefirst jacket, the metallic liquid thereby acting to transfer heatemanated from the first heat exchanger to the process steam.

There is further provided in accordance with the invention a highlyadvantageous sealing means particularly adapted to protection of thehigh temperature, highly corrosive solutions contemplated in theinvention against loss from process equipment having a motor drivenshaft entering through an equipment wall, the means comprising a blocksurrounding a wall-adjacent external portion of the shaft and havingspaced anular recessed adapted to receive first and second O-rings insealing engagement with the shaft and the block, the first O-ringsealing the process equipment; and a fluid channel between the recesses,and means to pressurize the channel and the O-rings with fluid inleakage-blocking relation through the first O-ring. The fluid channelfor pressurizing the first O-ring may extend spirally within the blockand coaxially with the shaft.

ORE REDUCTION APPARATUS

As noted above the invention contemplates simultaneously reducing metalbearing ore while oxidizing the fuel reactant. For this purposeapparatus is provided for the reduction of metal-bearing ore with highlyaromatic, refractory carbonaceous fuel residuals, the fuel residualsbeing dissolved in a molten salt solvent therefor, the apparatuscomprising a reactor defining a through-passage for the fuel residualsolution, means to disperse metal ore in the solution at temperaturesbetween 600° and 1000° C. and in reducing reaction proximity to the fuelresiduals for a time sufficient to substantially completely reduce theore to metal and to oxidize the fuel residual to gases. The apparatusmay further include means to recirculate the molten salt to and from thereactor, means to make fresh additions of fuel residuals to the salt,means to purge the salt of mineral matter beyond the reactor, means totreat gases produced in the process to derive the heat energy therefromincluding an expansion motor and means to pass the processed gases fromthe reactor to the expansion motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow sheet of the process showing majoroperations;

FIG. 2 is a more detailed schematic of the process;

FIG. 3 is a plan view, partly broken away, of the discoid reactoraccording to the invention;

FIG. 4 is a view in vertical section of the discoid reactor taken online 4--4 in FIG. 3;

FIG. 5 is a view in vertical section of the vertical reactor accordingto the invention;

FIG. 6 is a plan view, partly broken away to shown underlying parts ofthe ash and mineral matter removal apparatus;

FIG. 7 is a view taken on line 7--7 of FIG. 6;

FIG. 8 is a view in vertical section of vertical direct contact heatexchanger according to the process;

FIG. 9 is a view in vertical section of a discoid direct contact heatexchanger according to the process; and,

FIG. 10 is a view generally in vertical section of a high pressure sealaccording to the invention.

DETAILED DESCRIPTION Introduction

It is the purpose of the present invention to make practically usable inthe present social, economic and ecologic environment the vastquantities of residual carbonaceous fuel reactants derived from coalmining and petroleum processing. The ecological disposition of highlycarbonaceous fuel reactants has proved difficult within the constraintsimposed on fly ash, sulfurous gases and nitrogen oxide emissions andthis has limited the utility of several processes intended to obtainvaluable hydrocarbon products from coal. Thus in several of the knownprocedures for liquefying or gasifying sub-anthracite coal, thereremains after the relatively more reactive fraction has been convertedto the desired products, a residuum of refractory, less reactive highlycarbonaceous material which, practically speaking, must be burned oraccumulated for land fill or other less desirable purposes.

The present process and apparatus is adapted to taking up where existingtechnology leaves the coal or oil residual processor. By dissolving inmolten salt the char from coal pyrolysis or other highly carbonaceousresidual of coal or petroleum processing, and heating in accordance withthe invention, heat in a usable form is obtained, i.e. generally from 85to 98 percent of the heat output is in the salt matrix where it can beeconomicaly put to use in producing steam by appropriate heat transfersteps, also described herein, and thus relatively less heat is in thestack gases where extensive recovery is difficult and/or not economic.Meantime the coal or like residuum is substantially completely burnedleaving the salt available for reuse, following separation of ash andother solid e.g. sulfur products by techniques to be subsequentlyexplained herein. A further benefit of the salt matrix in addition toheat conservation and easy separation of ash and solid contaminants isfound in the catalytic effect of salt on the coal residuum combustionreaction. Thus although the salt is present in relatively large amountse.g. at least 2 and generally 4 to 6 times by weight as much salt ascoal or like residuum is present in the reactor, the salt exerts acatalytic effect which enables facile combustion of the residuum attemperatures below 1000° C. which temperatures disfavor formation ofnitrogen oxides, even when air is the gas used for combustion of theresiduum.

Additionally it will be observed in the ensuing description, that,throughout, speed of reaction of interaction is paramount enablingrelatively smaller apparatus than otherwise and heretofore thoughtnecessary for processing huge amounts of coal or like residuals.

The present process therefore integrates several procedures to achieve ahigh level of social benefit from coal. While the term "coal" will beused generally through the description herein as illustrative andtypical of the present process it is to be understood that "coal" hereinhas reference to coal per se i.e. high orders of coal e.g. anthracite,or to bituminous or sub-bituminous coals and coal derivatives i.e. coalswhich have been preprocessed to be substantially carbonaceous and highlyaromatic in their carbon character and more broadly to analogous coalderivative-like materials, as well to the crude oil or petroleumrefining residuals which are highly aromatic in their carbon character,as well. Returning then to the process, the objective is high volumetricefficiency and the low capital costs realizable thereby.

A typical steam-electric power generation plant reaches peak operatingcapacity during only a fraction of the time it is operated. The dailycycle may run for example from about 30% to 90% of peak capacity. Thefeed rate of e.g. a medium order of bituminous coal to produce steamfor, say, a 50 megawatt rated generator may typically vary from 1.575 to4.725 kg/second over a 30 to 90% of capacity operating range. Thus athree fold increase in generator load may require a corresponding threefold increase in fuel, where the feed to the steam generator is merelycoal. But it is possible to use much of the coal feed for higher valuepurposes such as chemicals production, without a commensurate change inpower production because while all of the coal feed may be used forheat, most of the heat is derived from the more refractory portion ofthe coal, while valuable chemicals may be derived from the lessrefractory, more volatile portions of the coal. For example, if the coalis first hydrocracked in advance of the steam generation step, valuablechemicals are obtained and the total coal feed change needed for a 30%to 90% ratio of power plant operating capacity is increased only 30%,and not trebled as when coal is only burned and not first processed forchemicals. Thus, assuming an operating rate of 30% of capacity the fuelfeed would be 10.5 kg/second where 85% of the feed is to be hydrocrackedfor chemicals and the balance used for heat production. At increasedoperating rates, e.g. to 90% the hydrocracking percentage can be loweredto 65% and the fuel feed need be increased only to 13.5 kg/second toaccommodate the increased use of capacity, that is only about a 30%change in feed rate over the lower capacity situation.

The high volume specific efficiency of the present system relative toconventional steam boiler operations makes it practical to replaceexisting steam boilers with a combination synthetic petroleum plant andsteam generator system which will have double the prior plant capacitybut not occupy any greater area than the existing plant site.

The present process incorporates ecologically important removaloperations e.g. sulfur compounds and ash well in advance of theexhaustion of gases to the atmosphere and at process points where theconcentration of these contaminants (unlike flue gases) is sufficientlygreat to make their recovery reasonable in cost and in some instancesself-supporting through sale of these byproducts or derivatives thereof.

Low capital investment and absence of air pollution are dual desideratain this invention and the former is realized in part through the use ofequipment designs which enable use of lower cost standard steels inconstruction despite 600° to 1000° C. temperatures in the reactor andheat exchanger. This is achieved by shielding the reactor supportstructure from reactor heat by a jacketing arrangement in which thejackets are filled with moving fluids used or useful in the process,which absorb heat emanated from the reactor, insulating the supportstructure and incidentally pre-conditioning system fluids and recoveringotherwise wasted heat. In this aspect of the invention the hightemperature, pressurized reactor chamber contents are thermally isolatedfrom the structural components carrying the support loads. Lower coststeels can be thus employed and at or near their load tolerances forordinary or ambient temperatures i.e. at or near maximum load factors.Higher cost, high temperature alloys need only be used for reactor wallsand the like.

In the description to follow the energy convervation objectives of theinvention are met not only through the use of jackets about thereactors, heat exchangers and piping to preheat the fluid inputs to thesystem, but also the enthalpy of the exhaust gases from the reactor isutilized to heat the input air or other oxidizer gas and/or drive aturbine, and the higher temperature components such as reactor andmineral (ash) separators are used for preheating fluids intended forsubsequent use including molten salt, molten metal and water/steamfluids.

CARBONACEOUS FUEL REACTANT

The terms "fuel reactant" and "carbonaceous fuel reactant" herein havereference to carbonaceous fuels such as coals including lignite,sub-bituminous, bituminous, subanthracite and anthracite coal, petroleumor coal derived coke, heavy petroleum residuals, tars and chars of coal,petroleum or materials of wood or agricultural origins.

COAL STRUCTURE

In the ensuing discussion reference will be to coal as typical andillustrative of the process feed material. Coal is a polymeric materialof extraordinary complexity and at the same time an abundant source ofnumerous carbon chain fragments. The present invention maintains asingle phase of molten salt solvent and coal polymer solute duringoxidation and, in preferred embodiments uses coal which has beenpretreated to free the relatively reactive portion of the coal moleculewhich is volatilized from the coal polymer complex e.g. from between 50and 85% by weight of a typical coal feed is thus relatively reactive.The less reactive, more refractory portion of the coal is not attemptedto be converted into volatile hydrocarbons, but is kept in solution andburned in a second reactor in accordance with the invention.

Within the combustion reactor, the less volatile e.g. polyaromaticmolecules and coal fragments, herein collectively referred to as coalresiduum or residual coal and representing the relatively non-volatile15 to 50% by weight of a typical coal is intimately mixed with anddissolved in molten salt.

ORE REDUCTION

Alternative to the use of an oxygen containing gas as the oxidizer incombustion apparatus is the use of non-gas forms of oxygen such as solidoxygen compounds. Particularly useful in this regard are ores of usefulmetals including specifically and notably the naturally occurring oresof Group VIII metals, most importantly iron and nickel ores. Thesematerials exist in great abundance in the United States but theseparation of the iron or nickel component is difficult and costly.Therefore the use of these ores as an oxidizer in the present processmeets this great need in a single step. Iron, or nickel is separatedfrom its ore by reduction, as char dissolved in molten salt is oxidized.The iron or nickel, freed from its oxygen bonding is collected from thecombustion reaction apparatus by separation from the salt, withconcomitantly less heat being recovered from the process overall.

ABSENCE OF NO_(x)

At this point another, environmentally significant advantage of thepresent process may be pointed out. Bearing in mind the fact ofcombustion of coal in the dissolved state in molten salt, and thecatalytic effect of the molten salt on the reaction, as well as the heatstorage capacity of the salt, the temperatures within the reactor areenabled to be kept below those temperatures (1000° C.) favorable to theformation of environmentally obnoxious nitrogen oxides (NO_(x)). ThusNO_(x) is avoided substantially, a uniquely advantageous benefit of thepresent process over conventional, non-solution coal combustionreactions.

COAL SOLUTION IN MOLTEN SALT

In preparing the coal or like carbonaceous fuel reactant for combustion,it is well to limit the phonomenon of outgassing which occurs whencombining coal with molten salt at temperatures above about 800° C. toup to 1200° C. In the present process, the coal is dissolved at lowertemperatures e.g. 250° to 500° C. up to about 600° C. and outgassing isavoided. In prior art processes using the aforementioned highertemperatures taught herein to be desirably avoided, pyrolysis of thecoal occurs, generating gas, the gas in turn forms a boundary layer onthe coal particle surface limiting access of the salt to the particle.This lessens solubilization which will otherwise occur and is a leadingcause of much of the prior art having to do with coal-molten saltsystems being limited to heterogeneous systems. As noted hereinheterogeneous systems are limited in combustion rate by surface reactionconsiderations. In the present process, the use of relatively lower(than pyrolysis) temperatures to achieve the initial coal solution,eliminates outgassing and produces a homogeneous solution which may bepassed to the combustion reactor directly or pretreated to recovervolatiles of value in the coal.

MOLTEN SALT SYSTEMS

The molten salt is inorganic, ionic and has a melting point below therange of reaction temperatures e.g. between 200° and 500° C. Mixtures ofsalts may be used, particularly to take advantage of eutectics. Anillustrative listing of useful salts and salt mixtures follows:

    ______________________________________                                                       ° C. Melting Point                                      KCl                                                                           BaCl.sub.2           345                                                      CdCl.sub.2                                                                             380                                                                  "                                                                             PbCl.sub.2                                                                             411                                                                  LiCl                                                                          PbCl.sub.2                                                                             410                                                                  "                                                                             SrCl.sub.2                                                                             475                                                                  NaCl                                                                          CdCl.sub.2                                                                             397                                                                  "                                                                             CoCl.sub.2                                                                             365                                                                  "                                                                             PbCl.sub.2                                                                             415                                                                  BaCl.sub.2                                                                    BeCl.sub.2                                                                             390                                                                  "                                                                             CdCl.sub.2                                                                             450                                                                  CdCl.sub.2                                                                    PbCl.sub.2                                                                             387                                                                  ZnCl.sub.2                                                                    SnCl.sub.2                                                                             180                                                                  "                                                                             SrCl.sub.2                                                                             480                                                                  MgCl.sub.2                                                                    PbCl.sub.2                                                                             460                                                                  PbCl.sub.2                                                                    BeCl.sub.2                                                                             300                                                                  "                                                                             BiCl.sub.3                                                                             205                                                                  "                                                                             CaCl.sub.2                                                                             460                                                                  "                                                                             CdCl.sub.2                                                                             387                                                                  "                                                                             CuCl     285                                                                  "                                                                             FeCl.sub.3                                                                             185                                                                  "                                                                             MnCl.sub.2                                                                             405                                                                  "                                                                             PbI.sub.2                                                                              310                                                                  "                                                                             SnCl.sub.2                                                                             410                                                                  "                                                                             TiCl.sub.4                                                                             390                                                                  "                                                                             ZnCl.sub.2                                                                             340                                                                  KBr                                                                           LiBr     310                                                                  I                                                                             CdBr.sub.2                                                                             325                                                                  "                                                                             MgBr.sub.2                                                                             350                                                                  NaBr                                                                          CdBr.sub.2                                                                             370                                                                  "                                                                             MgBr.sub.2                                                                             425                                                                  PbBr.sub.2                                                                    BiBr.sub.2                                                                             200                                                                  "                                                                             CdBr.sub.2                                                                             344                                                                  "                                                                             HgBr.sub.2                                                                             208                                                                  "                                                                             PbCl.sub.2                                                                             425                                                                  "                                                                             PbF.sub.2                                                                              350                                                                  "                                                                             PbI      282                                                                  ______________________________________                                    

It will be observed that typical salts are halides e.g. fluorides,chlorides, iodides and bromides of alkali, alkaline earth, Group II,Group IV, Group V, Group VII and Group VIII metals particularlypotassium, lithium, sodium, beryllium, barium, cadmium, zinc, calcium,lead, strontium, cobalt, bismuth, tin, copper, iron, titanium,manganese, mercury, and magnesium. Additionally, the hydroxides andcarbonates of alkali metals, being precursors of their salts, may beused, alone or in admixture with the aforementioned salts or othershaving appropriate melting points.

SALT MATRIX

Essential to the present process is the dissolution of the carbonaceousfuel reactant in molten salt. In general more than 2× and up to 100× asmuch salt as fuel reactant is employed, i.e. far beyond normallyconsidered "catalytic" amounts. For the purpose of this disclosure a"solution" is a dispersion of the fuel reactant solute in the moltensalt solvent to a degree that provides optical uniformity e.g. less than600 nanometers and preferably the largest aggregates are less than 300nanometers in diameter. In the solvent-solute systems of the processreaction proceeds on the molecular level, by attack of the oxidizer gason dispersed fuel reactant molecules, unlike certain prior knownprocesses where the fuel reactant is particulate. Thus combustion rateis highly dependent on specific surface. In a solution or homogeneoussystem the specific surface is orders of magnitude greater than inconventional heterogeneous systems i.e. particulate suspensions andreaction rate is therein limited to the particle surface reaction rate.

As a matrix for the combustion of carbonaceous fuel reactant, the moltensalt affords these advantages over the conventional fuel-air burner:First the salt retains both the ash and the sulfur normally generatedduring the combustion process. That is, the ash is not carried out ofthe reactor by the exhaust gases, eliminating a major source of airpollution and a cause of extra-ordinary expense in power plantconstruction. The sulfur may be separated by e.g. CaO or other reactant,without atmospheric exposure. Secondly, as noted above the salt has acatalytic effect on the overall combustion reaction catalyzing thecombustion to completeness and efficiently to reduce to negligibilitythe smoke and carbon monoxide generation otherwise associated withcombustion of such fuel reactants. Thirdly, also as noted earlierherein, the reaction temperatures of not generally above 1000° C. (1300°K.) are highly unfavorable to formation of nitrogen oxides. Thistemperature of reaction is to be contrasted with the 2700° - 3500° C.temperatures for certain other fuel-air systems. Fourthly, the bulk,i.e. over 50 percent of the heat of combustion reaction, is retaineddirectly in the latent heat of the molten salt matrix where it is easilyused to drive a heat engine. It will be recalled that molten salt hastypically 500 to 1000X the volumeteric heat capacity of combustionexhaust gases at 1 atmosphere pressure. More specifically, the instantmolten salt systems have specific heats of about 0.2 cal./gram/°C.Typical exhaust gases are approximately the same in specific heat.However, molten salts have a density more than 10³ times that of exhaustgases. Thus molten salts are by orders of magnitude, a more effectivemedium for transferring heat from the combustion process into a heatengine or other heat utilization device, than exhaust gases. Fifthly, asa function of the concentration of materials throughout the reactionzone, the characteristic dimension of the solution is likewise orders ofmagnitude smaller than is possible in the conventional fuel-air system,further enhancing the potential consumption of fuel.

In general the effect of dissolving coal fuel reactant in molten salt isto solvate the coal, swelling the coal polymer, and the cracking thereofto moieties of 250 to 25,000 molecular weight. A coal system with a meanmolecular weight of 2000 has more than 100,000× the specific surface forreaction as particulate coal even as small as 0.1 mm. mean diameter.Coal oxidation rates in molten salt suspension may be assumed to vary inproportion to specific surface raised to the 2/3 power, and thus theimportance of obtaining solutions reaction, as taught herein, ismanifest.

HEATER REACTOR -- DESIGN PARAMETERS

Specific apparatus has been devised and is described herein for theheater reactor, but it may be observed in general that in these and likecharacter reactors contemplated by the invention, the design parametersare (1) a controlled path of travel of fuel - molten salt solutionmixture through the oxidizer gas stream (2) extremely brief contacttimes e.g. residence or dwell times (defined as reactor chamber volumedivided by reaction mass flow rate through the reactor chamber) on theorder typically of 0.5 to 2.0 seconds; (3) extensive interdispersion offuel reactant and salt; (4) maximization of extraction of heat ofcombustion from the exhaust gases; (5) minimization of heat fluxemanations from the reactor to the structural supports of the reactor;(6) provision of sufficient air-oxygen for stoichiometric conversion ofC to CO₂. Thus one kilogram of fuel reactant-molten salt solutioncontaining 5% by weight carbon is provided with 0.66 kilograms of air torealize the stoichiometric ratio. Further one liter of fuelreactant-molten salt solution is provided with approximately one cubicmeter of air at standard conditions.

It has been found that the foregoing ratios and other designconsiderations are best realized by spraying the fuel reactant-moltensalt solutions countercurrently through a flowing stream of the air. Thebulk of the heat release, from combustion, occurs some distancedownstream of the inlet point of the molten salt solution, in general inthe last 20% or so of the solution travel path through the reactor. Thismeans that the "exhaust gases" i.e. those gases containing substantialquantities of heat from the last stages of reaction must traverse about80% of the reactor travel path before exiting the reactor and thesegases are in contact with the incoming molten salt solution all thewhile. Thus, the generated product gases have their heat reduced by theincoming salt solution droplets in coursing through the 80% of thereactor travel path. The combustion heat is thus kept in the reactor,and put into the salt, for recovery and use as will be explained.

A further heat management feature of the process is realized byjacketing the reactor and passing the incoming air feed over the reactorto acquire reactor emanated heat, for return to the reactor andprecondition the air for more efficient combustion.

In somewhat greater detail, the disclosed reactor designs optimize thesensible heat increase in the molten-salt matrix as the fuel reactant isoxidized, while simultaneously extracting as much heat as possible fromthe produced gases. The purpose of these reaction designs, therefore, isto maximize ΔH (of input salt solution to output salt) while minimizingΔH (of input gas to output gases). While the indicated reaction may becarried out in a simple "pot" type reactor with air being blown througha coalesced liquid molten salt solution, such a system is convenient touse where a high volume of air per unit volume of molten salt is desirede.g. a ratio of 1000× air at standard conditions relative to saltcontaining about 5% fuel. Flow rates of less than about 1% reaction persecond are required in a typical pot reactor to prevent simply blowingthe salt out of the reactor.

Accordingly, it is preferred in the present system to disperse themolten salt-fuel reactant solution into a multiplicity of droplets andto spray the droplets through an air stream. Typically and in oneembodiment hereof the salt solution is sprayed downwardly through anupdraft of air or other oxidizer gas. The spray may be formed byimpinging angularly directed and colliding jets of solution, by use ofswirl cones or shower-head type nozzles or like apparatus and techniquesfor breaking a stream into droplets. Stream break-up by whateversuitable method will provide a relatively fine spray dispersed into theoxidizer gas stream.

Considering the nature of the solution spray, the spray droplets willhave an initial spatial coordinate velocity from the momentum impartedfrom the vector components of the velocity of the injection streams. Anyindividual spray particle has a relative velocity to the gas streamwhich is the vector sum of the particle trajectory velocity and the gasstream drag forces. Each of the different spray developing techniquesmentioned above has its own characteristic pattern of break-up withdefined beginning and final break-up points, and a defined statisticaldistribution of spray droplet diameters. The mean droplet size anddistribution for impinging "fans" are computable through known formulaeas is the mass median droplet size for "shower-head" nozzle break-up byaerodynamic interaction.

Once the individual droplet is formed the process focuses on theutilization of three intersecting transport phenomena:

1. Momentum Transfer

As the droplet falls in the countercurrent air flow, the drag will slowthe droplet. Conventionally, droplets have been treated as sphereswherein the "drag force" has been equated to the droplet mass times itsacceleration to derive a drag factor C_(D). Values for C_(D) versusReynolds Number have been extensively measured and compare approximatelyas follows, in the range of interest:

    ______________________________________                                        Reynolds Number (Re)                                                                              C.sub.D                                                   ______________________________________                                        0.5<Re<70           27 Re .sup.-.sup.0.84                                     70<Re<59,200        0.414 Re .sup.0.14 3                                      59,200<Re           2.0                                                       ______________________________________                                    

The trajectories of the droplets of different size classes may becalculated. The initial drop velocity and the countercurrent gasvelocities are designated so that the fall vector of the droplet with aradius representing the 90th weight percentile will read zero verticalvelocity at a height between 80 and 100% of the fall distance. Afterthis point, the droplets will start to reascend until colliding andcoalescing with other drops, falling thereinto. This slowing of theother drops fall and recirculation of the drops occurs most extensivelyin the lower 10% of the reactor chamber length. The spray mass, thereby,will spend over half of its total fall time slowing and recirculating inthe lower end of the reactor chamber.

2. Mass Transfer

In order to carry out the combustion or more properly the oxidation ofthe dissolved fuel reactant, oxygen from the air must dissolve in themolten salt-fuel solution and the fuel and oxygen codiffuse intoreaction proximity. If the intradrop diffusion processes (inside thedroplet) are much faster than the transdrop diffusion (through the gasboundary layer), the reaction rate may be treated as gas boundary layerlimited. On the other hand, if the diffusion processes through the gasboundary layer are much faster than the intra-drop diffusion, thenintra-drop diffusion will be the limiting rate. If both transdrop andintradrop diffusion processes are of the same order, both processes mustbe considered in evaluating the reaction rate. Assuming an analogybetween diffusion and heat transfer for highly fluid droplets, it hasbeen shown elsewhere that for the assumed sphere, size and time regime,the distribution of heat is nearly uniform through the sphere. Furtherassuming the mentioned similitude between the heat transfer anddiffusion in a fluid drop, the reaction rate in oxidizing the fuel inthe droplet is determined by the diffusion rate of oxygen through thegas side boundary layer to the droplet. Existing mass transfercorrelation thus permits the estimation of oxygen influx, the combustionrate, and CO₂ efflux to and from the droplets.

3. Heat Transfer

As noted, the oxidative process occurs within the droplet of the moltensalt-fuel reactant solution. Thus the droplet is the site of heataccrual. The droplets will exchange heat with the surrounding gasenvironment by these processes:

(a) The largely carbonaceous fuel will react with the oxygen to yieldCO₂ on an approximately 1:1 basis. the CO₂ will have the droplet at theinstant drop temperature while O₂ influx arrives at ambient (for thereactor) temperature. The effect is a net increase in the reactor gastemperature;

(b) Forced convection heat flux will have two effects. First the heatflux will heat up the incoming gas flow at the bottom (inlet) of thechamber where, as mentioned, the bulk of the oxidative reaction hasoccured, to heat up the droplets. Secondly, the heat flux will cool theheated, oxygen depleted exhaust gas flowing upward through theyet-to-react droplets in the upper 80% or so of the reactor chamber.

The heat flow due to the exchange of local gas ambient temperature O₂for droplet temperature CO₂ can be estimated from diffusion correlationsand the correlation for forced convection heat flux from other equationsto permit a computation of heat flow values for the process.

There is disclosed herein apparatus executing the principles justenunciated and designed to obtain high rates of energy release from theair-oxidation of molten salt-carbonaceous fuel reactant solutions.Specifically apparatus herein described enables hot exhaust gasesproduced adjacent the salt outlet- and air inlet-area of the reactor toexchange heat and momentum with the counterflowing droplet field,reducing the droplet speed to near zero-relative to any fixed point inthe chamber, and reducing the exhaust gas temperature to near that ofthe molten salt fuel reactant solution inlet temperature (400° - 600°C.).

Treating now with more specificity the jacketing concepts for thereactor which enable use of low cost steels for support work at thereactor, the apparatus reactor chamber may be double-walled or enclosedby tubular members to surround or "jacket" the reactor per se. Thejacket (be it a walled chamber or a plurality of tubes) is filled withmoving fluid at a temperature above the melting point of the molten saltbut below the reactor chamber reaction mass temperatures. This jacketfluid in certain embodiments is the molten salt itself, e.g. at reactorchamber inlet temperatures (below 600° C.) or in other embodiments ametallic liquid, molten lead or high temperature organic heat exchangemediums such as diphenyl oxide. Beyond the jacket just described thereis provided a second double wall or tubular layer through which air feedis flowed at temperatures approximately 280° C. Thus the structuralmembers supporting the reactor chamber and containing the pressure loadthereof being exterior of the jackets are not subjected to thermal loadsmuch beyond 250° C., despite the reactor chamber interior reachingtemperatures of nearly 1000° C.

HEAT EXCHANGER DESIGN PARAMETERS

It is a signal feature of the present process that heat managementtechniques have been developed and are presented here which complementthe innovative combination reactor and process and enable the obtainingof the full benefits of this technology. As will be noted from thediscussion of the combustion reactor, the purpose there is to obtain asmuch heat as possible and to get as much heat obtained as can be intothe salt. The present portion of this disclosure is concerned primarilywith getting utility from the heat in the salt.

Several criteria have been developed for establishing heat exchangerdesign including:

1. Direct contact heat exchange between fluids of different temperature.

2. Use of mutually immiscible fluid pairs, each with good Δp.

3. Use of jacketed apparatus.

4. Avoidance of cross contamination between the heat producing fluid(salt) and the heat using fluid (steam).

In general the heat exchange is accomplished by using a two-phasedifferential flow, high dispersion, high relative velocity fluid-fluid,direct contact heat exchanger system. Among the several advantages ofdirect contact heat exchangers over indirect heat exchangers are:

(a) From one to four orders of magnitude greater specific surface;

(b) From one to four orders of magnitude shorter mean molecular pathsfrom any point in the heat exchange fluid to an exchange surface

(c) Absence of separating walls which reduce heat flux.

As in the reactor designs above noted, heat exchange construction withjacketing permits the components of the vessel structure which bear thedesign stresses to function at a temperature substantially below thetemperatures of the exchanger fluid content. The result of thesecombined design features is a heat exchange system adapted to beinterposed between a heat source and a heat consumer of heat engine suchas a steam turbine and by its design the heat exchange system is ordersof magnitude smaller than a conventional steam plant boiler system ofcomparable output rating and being smaller it consumes fewer materialsin its construction and costs less.

PRINCIPLES OF HEAT EXCHANGERS

The majority of heat exchangers have fixed surfaces over or throughwhich a fluid moves to add or remove heat. Frequently the solid surfacesare walls which separate two moving fluids and confine them along apredetermined path while a heat flux occurs between them. Direct contactheat exchangers are known e.g. evaporative coolers which comminglefluids but in these the fluids are exhausted and continually replaced.

In a conventional heat exchanger of the confined path type, volumetricspecific heat flow is severly constrained by the practicalities ofconstruction geometry which limit the surface area which is availablefor heat transfer operations. And the less surface area, the lower rateof heat transfer other factors being equal, and the larger the heatexchanger needs to be to accomplish the transfer of a given quantum ofheat in a given period of time.

RECOVERABLE FLUIDS HEAT TRANSFER

In contrast to surface indirect heat exchangers and heat exchangers ofthe evaporative cooling type, the present process utilizes fluid whichare intimately mixed to effect heat transfer, but which being inherentlyimmiscible, are recoverable and indefinitely reuseable. Importantly theheat transfer medium is highly dispersible to maximize heat transfersurface, but also readily recoalesced for ease of manipulation throughthe process. Thus the heat exchangers of the invention employ heat fluxpreferably between two immiscible, separable liquids, in generalincluding a differential passage of one liquid past the other, e.g. theheavier liquid downward, the lighter liquid upward, with intimateinterdispersion between the respective liquid inlets and outlets. Thereis subsequently described herein specific apparatus for the purpose, butat this point it may be observed that such apparatus lends itself toincorporation in a high volume, high efficiency power plant such as thatdescribed herein deriving high heat energies from combustion of certainfuels dissolved in molten salt, using the high heat content salt as oneof the heat transfer fluids.

Therefore the present invention avoids the limitations of indirectcontact heat exchangers, specifically by eliminating the walls whichdefine separate fluid flow paths, and which as well limit heatconduction and restrict the surface area available for heat transfer.Further said prior art heat exchangers provide heat transfer betweenfluids only at the wall-interface which is by nature far from the bulkof the fluids in order to permit adequate flow rates. Only evaporativespray coolers and certain rocket motors have achieved the near ultimatein high volume specific phenomena rates, and because these systemstolerate an ultimate commingling of the fluids; but the fluids arenonrecoverable, and such systems have not been adapted to power plantheat transfer applications where fluid recycle is economically essentialor where fluid contamination is intolerable, such as steam fluid forturbines.

As will be described hereinafter in greater detail, there is providedherein a novel construction of a heat exchange system in which a pair ofheat exchangers are used, and coupled together in the heat transfer andphysical sense by a nonmiscible, inert heat transfer fluid specificallyin most preferred embodiments, liquid, molten lead. The use of thisintermediate heat transfer medium enables utilization of a directcontact fluid-fluid heat exchange with all its attendant benefits, andwithal avoids cross-contamination of the fluids. This heat is taken fromthe molten salt into the heat transfer medium and transferred from theheat transfer medium into steam, without the salt contacting the steam.As will be evident this technique of heat transfer permits use of systemdesigns utilizing very high specific contact surfaces (molten leaddistributed in molten salt and molten lead distributed in steam) andvery high flow Reynolds numbers to thereby yield high efficiency designsfor the transfer of heat from molten salt to steam to drive heatengines, such as turbines.

Specifically the present apparatus and process comprise a direct contactfluid-fluid heat exchange system using high dispersion contact, andmutual immiscibiiity and density differences to effect a cleanseparation of the fluid into separate effluxing streams. In a verticalapparatus, the higher density fluid is introduced at the upper end ofthe heat exchanger chamber e.g. injected thereinto to flow in a highlydispersed, high shear manner downward through the chamber. This heavierphase falls in its dispersed condition until collected at the interfaceof the dispersed droplets and the coalesced mass of droplets, at or nearthe bottom of the chamber. The heavier phase is a continuous phase atthe chamber bottom and may be recycled and redispersed. The lighterdensity fluid is introduced into the same heat exchanger chamber at thelower end thereof e.g. injected to pass upwardly in a highly dispersed,high shear flow relation through the continuous phase portion of theheavier fluid to the mentioned interface of the heavier fluid dispersedand continuous phases, through that interface, whereupon the lighter,upwardly moving phase itself coalesces from its initial dispersion andbecomes the continuous phase through which the heavier phase movesdispersed. In a vertical chamber embodiment, the force of gravity isused to effect relative movement of the heavier and lighter phases,facilitated by preferably large differences in density of the fluidsbeing passed differentially through the chamber. It will be apparentthat movement of the two phases in the same direction, but at differentspeeds will also effect the differential passage of fluids. In certainembodiments, the separation of phases may be accelerated or clean-up ofphases made more complete, particularly where fluid density differencesare smaller, by passing the respective effluents through e.g. cycloneseparators as a supplemental step.

In other embodiments, the heat exchanger chamber may be essentiallyhorizontal and disc-shaped or "discoid." In these embodimetns thedifferential fluid passage is enhanced by centrifugal forces and gravityforces are essentially neglected. Centrifugal forces are realized by aninduced rotary movement of the two fluids. Typically the lower densityfluid is injected near the outer collecting volute rim for the higherdensity fluid and passed centripetally inward, while the higher densityfluid which has been introduced radially adjacent an axially locateddischarge port for the lighter phase is passed centrifugally outward. Inthe embodiment, the two fluids rotate in the same direction; thecentrifugally induced "g" field forces a countercurrent i.e.cross-current flow, of the lower density fluid inward to the axis andthe higher density fluid radially outward toward the chamber periphery.As in the vertical embodiment, the respective fluids are first dispersedin a continuous phase of the other and they coalesced for recovery andto define the continuous phase to receive the dispersed phase adjacenteach fluid inlet.

Accordingly there is provided herein a method and apparatus for directcontact heat exchange. Specifically there is provided a method for heatexchange between a relatively higher density liquid and a relativelylower density liquid immiscible therewith and having different heatcontents, which includes differentially passing a dispersed phase ofeach liquid through a continuous phase of the other liquid in a heatexchange zone, and coalescing the dispersed phase liquids so passed todefine the continuous phase of that liquid. The method further includesinitially dispersing the first liquid in the continuous phase of thesecond liquid and subsequently the second liquid in the continuous phaseof the first liquid, and subjecting the liquids to a forcedifferentially urging the dispersed phases past one another and intoself-coalescing proximity beyond the continuous phase of the liquid inwhich the dispersed phase was initially dispersed. In practice of themethod, the coalescence of the higher density liquid continuous phasedisplaces the lower density liquid continuous phase within the heatexchange zone. That is, when the heat exchange zone is verticallyextended and the urging force is therefore gravity, the lower densityliquid continuous phase is displaced upwardly, whereas in a circularzone where the force is centrifugal the lower density liquid isdisplaced centripetally. In apparatus terms there is provided for directcontact heat exchange, a chamber having means to pass relativelyimmiscible, different heat content different density liquidsdifferentially in direct contact through the chamber and means torecover each of the liquids separately, in continuous phase andsubstantially free of the other liquid. The chamber may further beprovided with inlet means adjacent the outlets for each continuous phaseliquid to introduce the other liquid in dispersed phase relation intothe continuous phase. Where the chamber is vertically elongated, theinlet for the lower density liquid will be at the bottom and the outlettherefor at the top of the chamber, the inlet for the relatively higherdensity liquid conversely being at the top and its outlet at the bottomof the chamber. Where the chamber is discoid, the chamber has aperipheral inlet for the relatively lower density liquid and centraloutlet therefor, and conversely, a central inlet for the relativelyhigher density liquid and a peripheral outlet therefor.

DESPERSION ASPECTS

As noted the two fluids are dispersed into continuous phases of oneanother and then collected as a continuous phase subsequently. Thetechnique of dispersion of the phases may involve one or both ofinjection and stream break-up by impingement of angularly directedcolliding streams which "fan" into droplets, or use of injection nozzlesof appropriate design e.g. "shower head" injectors. Whatever the mode ofbreak-up of the fluid streams into droplets and upon calculation of themean drop size from available formulae for similar systems the droplettrajectories may be estimated, initially from the injection vectors andmore specifically from consideration of drag and momentum transfersincluding incremental transfers of momentum, residual momentum and thecontinuingly exerted forces i.e. gravity in the vertical chamber orcolumn and centrifugal forces in the discoid chamber. The momentumchange in the discontinuous phase is estimated from the "dragrelations," plus the effects of gravity loading or centrifugal loadingin these respective, affected chambers.

HEAT TRANSFER ASPECTS

Heat Transfer between the droplets of the discontinuous phase and thesurrounding continuous phase occurs under "forced convection"conditions, estimable from known correlations of heat flux transfer tospherical droplets. The result of droplet forced convection, heat fluxtransfer relative to conventional heat exchange system is that thepresently disclosed heat exchangers, have:

(1) Orders of magnitude greater specific surface for the heat fluxfluids; and

(2) Orders of magnitude shorter heat flow paths from any given point inthe heat exchange fluid to a heat exchange interface of discontinuousphase droplet and continuous phase matrix.

JACKETED APPARATUS

In the reactor construction design, the heat exchangers of the inventionare double-walled, tube lined or otherwise jacketed to have an innershell containing the high temperature fluids (up to 1000° C.) with anegligible Δp across the shell, and withal a support or load carryingstructure which can function at hot side temperatures less than 200° C.Thus the heat exchangers herein are substantially reduced in weight,size and materials cost and can operate at relatively higher pressuresand/or temperatures for a given set of construction materials.

HEAT EXCHANGE MEDIUM

The several criteria for the heat exchange medium include (1) fluidityin the temperature range of interest, (2) inertness to constructionmaterials, and relative to the heat transferring fluid: (3)immiscibility; (4) substantial differences in vapor pressure at theseveral operating temperatures encountered; and (5) relatively differentdensities, particularly where separation is being effected by gravity orcentrifugal field forces.

Among the materials which may be mentioned for use as the heat transfermedium, relative to the other fluids being processed are highly reactivemetals such as sodium, lithium and potassium which may be heat exchangedwith saturated hydrocarbons in thermally stable regimes; somewhatreactive metals exchanged with nonreactive molten salts; water which maybe exchanged with various nonreactive liquids; low reactivity gases forheat exchange with other low volatility, low reactivity liquid; and in apreferred group low reactivity low melting metals, particularly lead,bismuth, tin and their alloy systems, which may be heat exchanged withwater (steam) fluorocarbons, nonreacting molten salts, numerous organicheat exchange liquids such as diphenyl oxide, and silicone oils.

In general for a given system of molten salt containing heat to betransferred to steam, it is preferred to employ a different density,high specific heat, immiscible liquid and particularly a metal and moreespecially lead or other high density, high specific heat, low melting,inert, nonreactive elemental or alloy metallic material such as tin orbismuth and particularly the lead alloys of these two metals.

DETAILED PROCESS AND APPARATUS DESCRIPTIONS

With reference now to the accompanying drawings, in FIG. 1 an overviewof the several operations is provided. Air as a typical oxidizer gas isintroduced into the process with preheating and precompression as willbe seen (FIG. 2) along line 10 to combustion reactor 12. To the samereactor 12 is introduced along line 14 a molten salt solution of fuelreactant, typically a coal residuum, or devolatilized coal product. Thefuel reactant is oxidized by the air fed into combustion reactor 12 andthere is obtained exhaust gases of the combustion and molten salt nowsubstantially coal free but containing mineral materials hereincollectively referred to as "ash." The salt is passed along line 16 forprocess use and ultimately venting to the atmosphere (line 48 in FIG.2), and the ash being separated therefrom along line 20 e.g. byapparatus hereinafter described with reference to FIGS. 6 and 7.Specific embodiments of the combustion reactor 12 are shown in FIGS. 3,4, and 5. Following separation from reactor 12 through line 16 the saltcarrying most of the sensible heat of combustion is heat exchanged toproduce steam by a series of heat transfer operations illustrated inzone 22, from salt, to liquid metal, to steam and recycled through line23. Additionally, the liquid metal heat is used for air preheating alongline 24 and the steam is cycled to steam consumer operations such as apower turbine (not shown) along line 26. Exhaust gases are removed vialine 18.

With reference now to FIG. 2, a schematic flow sheet of the process isset forth. The fuel reactant feed is introduced at 14. The nature andcomposition of the molten salt solution of the several useful fuelreactants has been discussed in detail above. The molten salt solutionfeed in line 14 is typically at a temperature between about 850° and1100° C. and preferably 900° and 1000° C. and at a pressure of betweenabout 1 and 15 atmospheres, the specific pressure varying somewhat withthe particular pressure conditions within the reactor 12, and the modeof delivery intended to be used in the reactor e.g. the type nozzles 27.In the FIG. 2 embodiment, the reactor 12 is a vertically extendedcylinder 28 operated nearly hydraulically full with a head space 30 atthe top of the cylinder, and a liquid level 32 just above the point ofintroduction of feed solution to the reactor so that the feed solutionis introduced from line 14 submerged. Hot gases are exhausted from thereactor head space 30 overhead through line 34 to successive heatexchange stages 36, 38 to derive the maximum benefit from the heatcontent of these gases, which heat content, is will be recalled, isgenerally less than half the heat of combustion and preferably far less,the vast bulk of the heat having been transferred to the salt 40 withinreactor 12. Nonetheless, the exhaust gases in line 34 do contain usefulamounts of heat. It needs to be recalled here that these exhaust gasesdo not require precipitators or like fly ash removal treatments, or evensulfur compound recovery operations, since these atmosphericcontaminants are trapped within the salt matrix 40 in the reactor 12 forsubsequent separation without ever becoming airborne.

The exhaust gases in line 34 are typically at a temperature between 400°and 500° C. and a pressure between about 1 and 15 atmospheres. Theseexhaust gases are passed through heat exchanger 36 for transfer of gasheat to incoming air feed to the reactor in line 10. From heat exchanger36, the somewhat cooled, but still hot exhaust gases are passed alongline 42 to an expansion motor, shown as turbo-expander 44, the hot gasesbeing fed into the expansion horn at 45, expanded therein e.g. to apressure of about 1 to 2 atmospheres and simultaneously cooled to atemperature between about 150° and 200° C. and passed therefrom alongline 46 to the further heat exchange stage 38 after which heat transfer,the exhaust gases are vented to the atmosphere through line 48.

Incoming air as the oxidizing gas is both heated and compressed inadvance of the reactor 12, using the exhaust gases. Thus air introducedinto the system in line 10 is passed into the compressor stages 50 ofthe turbo-expander. That is turbo-compressor 50 is operatively coupledto the expansion motor 44 as shown by dashed line 52 whereby the energyderived from the exhaust gas expansion is used to drive the compressorturbine. The air in line 10 is generally heated to between about 250°and 350° C. by this step and elevated in pressure from one atmosphere tobetween about 2 and 15 atmospheres. Following its compression andattendant heating in turbo-compressor 50, air in line 10 is heatexchanged with the exiting exhaust gases in heat exchanger 38 and heatexchanger 36 which define progressively higher temperature zones toincrease the temperature of the incoming air in line 10 leading to thereactor 12 between about 275° and 375° C. The air, at a pressure ofabout 2 to 15 atmospheres then is introduced into the molten saltsolution through a series of submerged inlets, nozzles 27, whichdistributively pass the air into the salt solution. Reaction ensuesbetween the heated, precompressed air and the molten salt solution offuel reactant. The exhaust gases are collected and employed as justdescribed.

It will be observed that the flow of salt solution and air through thereactor has been countercurrent, and too this flow is very rapid,providing quite limited residence times within the reactor 12 of on theorder of 0.2 to 2 seconds. The relative quantities of reactants are suchthat complete combustion of the fuel reactant is effected, and generallyin the ranges noted earlier in the description or higher or lower forparticular reactor, reactant and reaction situations.

The molten salt following removal therefrom by combustion of the fuelreactant and the concomitant generation of ash is passed out of thereactor 12 along line 16.

The molten salt in line 16 is generally at a temperature between 850+ ad1100° C. and a pressure of 2 to 10 atmospheres. The molten salt ispassed through the ash separator 54 to be described, where ash ismechanically removed and separated through line 56. The molten saltstill carrying its burden of combustion heat is passed to the heattransfer stages of the process. It may be desirable at this point toincrease the pressure on the molten salt to accommodate the pressurerelationships of the heat exchangers to follow. This may be accomplishedalong line 58 with state of the art booster pumps (not shown) includingsuch pumps driven by a pressure drop taken on process fluids fromelsewhere in the process.

It is generally desirable where steam is to be the ultimate end productof the process, to have the pressure of molten salt in line 58 between10 and 50 atmospheres for commencing heat transfer operations. Thisenables a pressure drop through the heat transfer steps while stillobtaining heat transfer to steam at useful pressures for operating agenerator turbine.

The molten salt in line 58 at a pressure between about 10 and 50atmospheres and a temperature between 850° and 1100° C. is passedthrough direct contact heat exchanger 60 (to be described in detailhereinafter) and exits the heat exchanger through line 64 at a pressureof about 5 to 45 atmospheres and a temperature between about 425° and475° C. The molten salt may be recycled along line 64 e.g. to thereactor 12 with a fresh charge of fuel reactant, as the solution feed.

Within the heat exchanger 60, typically and illustratively, a liquidmetal introduced at a temperature of 350° to 400° C. and a pressure of10 to 50 atmospheres from line 66 acquires heat by direct contact heatexchange from the salt, to exit the heat exchanger at 800° to 1000° C.and a pressure of 5 to 45 atmospheres. Thus heated, liquid metal, freeof salt, is passed along line 68 which together with line 66 comprises aclosed liquid metal loop, to a further direct contact heat exchanger 70wherein steam is heated by direct contact with the liquid metal.Following heat transfer in heat exchanger 70 the liquid metal isreturned to salt heat exchanger 60 for reheating, along line 66 of theliquid metal loop. The steam from heat exchanger 70 is passed along line72 to a turbo-generator 74 e.g. a conventional steam driven turbinegenerator for the generation of electricity, and thence returned forreheating to the liquid metal heat exchanger 70 through line 76, thelines 72 and 76 defining a steam loop. In general, the steam beingintroduced into the liquid metal heat exchanger is at 50 to 200atmospheres pressure and 100° to 150° C. temperature, while the metalexchange heated steam in line 72 is typically at 650° to 800° C. and 45to 190 atmospheres.

VERTICAL REACTOR DESCRIPTION

In FIG. 2 a vertical reactor 12 operated hydraulically full of moltensalt is illustrated. In FIG. 5, a preferred form of vertical reactor 121is depicted, one providing for the suspension of fuel reactant-saltsolution in an updraft of air or other oxidizing gas for the requiredtimes to completely oxidize the fuel reactant. Additionally, numerousheat management features are integrated into the FIG. 5 reactor design.With reference then to FIG. 5, the reactor 121 comprises a reactorchamber 80 defined by vertically extended cylindrical wall 82 havingcentral openings 84 at the top and 86 at the bottom thereof for anexhaust gas outlet pipe 88 and a molten salt outlet pipe 90respectively. The wall 82 is generally enclosed by a first jacketstructure comprising coaxial cylindrical wall 92 defining with reactorchamber wall 82 an inner annulus 94. The reactor chamber 80 and theinner annulus 94, in turn, are enclosed by a second jacket structurecomprising the cylindrical coaxial wall 96. Wall 96 defines with thefirst jacket wall 92 an outer annulus 98. An inlet port 100 extendsthrough the upper portion of the wall 96 of outer annulus 98 forintroduction of fluid into the inner annulus 94. The inner annulus 94terminates in an outlet 102 coaxial with molten salt outlet pipe 90.

A series of circularly spaced injector ports 104 is provided about thelower reaches 106 of the reactor chamber 80, communicating the lowerchamber interior 106 with the outer annulus 98. An annular, downwardlyextending baffle 108 surrounds the lower reaches 106 of the chamber 80,ensuring passage of fluid in the outer annulus 98 all along the lengthof the first jacket wall 92 prior to entry through injector ports 104.There is additionally provided a salt-fuel reactant solution distributor110 at the upper end of the reactor chamber 80. Typically the solutiondistributor 110 will include an array of downwardly directed nozzles 112supplied molten salt solution with fresh fuel reactant dissolved thereinfrom inlet line 114.

The vertical reactor 121 is operated by introducing a 5 to 20 percentsolution of e.g. coal in molten salt at a temperature of 400° C. and apressure of 10 atmospheres through nozzles 112 in a downwardly directedfree-falling spray 116. Air or other oxidizing gas is passed from line118 through annulus 98 along the length of the reactor 121, increasingin temperature by indirect absorption of heat emanating from the reactorchamber 82 (and simultaneously protecting reactor chamber supportstructure, not shown, from undue heat exposure) to be at a temperatureof 250° C. and a pressure of 10 atmospheres at the injector ports 104.The introduced gas 122 generates an upward draft which carries thefalling molten salt droplets dancingly up and down in the reactorchamber 80, generally at the lower 20 percent of its length e.g. at 108,as heretofore described, until the coal therein is consumed and the saltdroplets agglomerate and coalesce sufficiently to fall through the gasupdraft. Coalesced droplets are collected in a pool 120 in receptacle124 for separation from the reactor chamber 80 through pipe 90.

The liquid metal, or like heat exchange medium, used elsewhere in theprocess for direct heat transfer is employed in the FIG. 5 reactordesign as an indirect heat transfer medium. Liquid metal, such as lead,is passed through inner annulus 94 between the reactor wall 82 and thegas in outer annulus 98, to simultaneously limit heat emanation from thereactor chamber 80 to surrounding structure, to preheat the oxidizer gasfeed from line 118 and/or to heat the liquid metal for other operations.

Exhaust gases produced are taken from the chamber 80 through pipe 88 forhandling as earlier described in connection with FIG. 2.

DISCOID REACTOR DESCRIPTION

Alternative to the vertical reactor of FIGS. 2 and 5 is the discoidreactor 221 shown in FIGS. 3 and 4. The discoid reactor 221 partakes ofthe same principles of differential flow of oxidizer gas and molten saltsolution, and multiple jacketing of the reactor as are found in the FIG.5, reactor 121 embodiment. Thus, with reference to FIGS. 3 and 4,discoid reactor 221 comprises a generally cylindrical horizontallyextended chamber 200 defined by a radially tapered wall 202 having anaxial passage 204 extending upwardly therefrom. The discoid chamber wall202 is generally enclosed by a congruent wall 206 which together withthe chamber wall defines inner interwall space 208. Beyond wall 206 is afurther wall member 210 which also is generally congruent with thechamber wall 202 and which with wall 206 defines an outer interwallspace 212. The inner interwall space 208 defines a flow space for liquidmetal or other heat transfer fluid being used elsewhere in the processand which is passed along the chamber wall 202 between inlet port 214adjacent the chamber axis 215, and outlet pipe 216 at the perimetricalextremity of the reactor chamber 200. Air, or other oxidizing gas, isfurnished to the discoid chamber 200 through a series of relativelycircularly spaced injector ports 218 which communicate the interior ofchamber 200 with the outer interwall space 212 into which air or othergas is introduced through inlet 220. For purposes to appear the injectorports 218 are canted relative to the median horizontal plane of thechamber 200. As in the vertical reactor 121 the discoid reactor 221 isprovided with a baffle 222 to ensure full passage of the feed air alongthe entire extent of the reactor chamber wall 206.

In the discoid reactor embodiment of FIGS. 3 and 4, the molten salt-fuelreactant solution may be introduced by a series of nozzles andpreferably is introduced through inlet 217 at nearly the axis 215 of thereactor chamber 200 and in a series of angularly directed, colliding,jets or streams 219 which, upon impingement, fan into a multiplicity ofdroplets to ensure break-up of the solution into readily treated,discrete portions. For this purpose the discoid chamber 200 is providedwith a series of opposed pairs of angularly related jet nozzles 224 fedby upper and lower plenums 226 to generate a fan of the dropletizedstreams 223. The nozzle 224 like the air ports 218 are canted relativeto the median horizontal plane of the reactor chamber 200, for purposesnow to be explained.

The relationship of the several fluid streams is highly important.Initially, it will be observed that differential, counter-flow isrealized by introducing the molten salt fuel reactant solutioncircularly and adjacent of the chamber axis 215 through canted nozzles224 which direct the solution circularly into the chamber 200 i.e.tangent to a line parallel to the chamber periphery 230 and salt istaken out at the chamber periphery through pipe 232. Air, as theoxidizing gas, is introduced at nearly the periphery 230 of the chamber200 and exhaust gases are taken off at the axis 215 of the chamber 200.Thus, these two fluids pass through one another. The air, before beingintroduced into the reactor chamber 200 is passed radially outwardthrough outer interwall space 212 to absorb, indirectly, the heatemanated from the combustion occurring in discoid chamber 200, whileliquid metal similarly is passed concurrently from nearly the chamberaxis, at inlet port 214 to the periphery 230 of chamber 200 for exitthrough pipe 216; the liquid metal absorbing the reactor chamber heatindirectly through chamber wall 202 and transferring some of this heatindirectly to air or other oxidizer gas to be introduced into thereactor chamber 200 through injector ports 218.

The flow pattern of salt-fuel reactant droplets 223 is determined bytheir canted disposition and the relative location of their inlet 217and outlet 232, and the prevailing flow direction of air or like gas inthe discoid reactor chamber 200. Recalling the suspension of droplets inthe vertical reactor 121, it will be clear that the gravity force on thedroplets 116 there was balanced at least briefly, and in a dynamic wayby the force of updraft air 122. Similarly, in the discoid reactor 221the air force balances, briefly and dynamically, the force carrying thedroplets from the point of introduction to the point of exit. For thispurpose, the air injector ports 218 are canted so as to give aninitially circular or more particularly, spiral, flow path to theinjected air. In FIG. 3, this spiral air pattern is shown in the lightdashed lines 236. Salt solution droplets entrained in the air stream,are carried therewith, but as they acquire speed, centrifugal forcescome into play carrying the droplets outward along a different spiralpath, a path of greater spiral pitch than the air streams 236, anillustrative path being shown by the solid line 238. As the dropletloses fuel reactant and becomes lighter, the centrifugal force isdecreased relatively, but the angular velocity of the air streams at theperiphery 230 of the reactor chamber 200 is less relatively thaninwardly of the periphery, the result being a dynamic suspension of thedroplet, for a time enabling complete combustion of the fuel reactant,and coalescence of the droplets to a mass sufficient to separate fromthe air stream into peripheral pool 240 for separation through outletpipe 232.

The temperatures and pressures of the several fluids in the discoidreactor embodiment of FIGS. 3 and 4 are the same generally as thesevalues in the vertical reactor embodiments of FIG. 6.

REMOVAL OF ASH AND OTHER SOLIDS

It has been pointed out above that mineral matter remaining aftercombustion of the coal or like fuel reactant which matter may begenerally referred to as ash and will include all manner of solidsubstances including oxides and sulfides of metals including for examplealkali metal sulfides produced by addition of alkali metal salts andhydroxides. With reference to FIGS. 6 and 7 an ash separator 250 isshown comprising a chamber 252 of generally circular design andcentrally domed. The chamber 252 is supported on hollow post 254 whichextends upward into the interior 256 of the chamber above the horizontalmedian level within the chamber, for purposes to appear. To one side ofthe chamber 252 at the median level of the chamber a barrel 258 isprovided extending horizontally through the chamber to open at 260 onone side into the chamber. Barrel 258 is provided with a rotatable screw262. Additionally an inlet 264 for delivery of ash containing moltensalt (i.e. from line 16 in FIG. 2) is provided generally diametricallyopposite the barrel 258 and aranged to deliver the molten salttangentially into the chamber 252 whereby the salt assumes a circular,or more properly a spiral flow path through the chamber. The post 254 isopen at the top to define a salt outlet 266 communicating with thehollow interior 268 of the post and ultimately to line 58 (FIG. 2) forflowing the ash-separated molten salt to the heat exchange stages.

In operation the spirally flowing molten salt imparts a relativelygreater centrifugal moment to ash and like mineral solids suspended inthe salt whereby these materials are carried to the periphery 270 of theash separation chamber 252. Screw 262 is rotated to urge peripheralaccumulations of ash and entrained salt from the chamber 252 todisposal. The molten salt is passed from the chamber 252 centrallythrough opening 266. Opening 266 is at a height within the chamber 252that limits carryover of ash with the molten salt passing through theopening to provide an effective decanting of molten salt from ashaccumulations and continual purging of the chamber of the ashaccumulation by screw 262.

As shown, the ash separator 250 is jacketed by wall 272 so as to recoverthe heat of the molten salt, e.g. into liquid metal or steam to be usedelsewhere in the process, by passing these fluids over the chamber 252exterior.

In a typical instance of the process, the molten ash and salt mixture inline 16 enters separator 250 at a temperature between about 850° and1100° C. and at a pressure between about 2 and 10 atmospheres. Themolten salt, now ash free leaves separator 250 with little loss oftemperature or pressure.

HEAT TRANSFER TO STEAM -- VERTICAL EXCHANGER

The principles of heat transfer from molten salt to a dispersed highspecific heat, inert heat transfer medium and from that medium to steamhave been discussed above. With reference to FIG. 8 a form of apparatusfor effecting the transfer of salt heat content to a liquid metal suchas molten lead is shown at 300. The apparatus 300 comprises a verticallydisposed elongated chamber 302 having a wall 304 of generallycylindrical configuration and domed at the top and bottom. The chamber302 has a molten salt inlet pipe 306 leading e.g. from line 58 (FIG. 2)and a series of laterally distributed nozzles 308 for delivering thesalt into the chamber interior 310 as a discontinuous phase in moltenmetal for passage upward through the chamber. In general, the moltensalt delivered to the chamber 302 is at a temperature between about 850and 1100° C. and a pressure of 10 to 50 atmospheres. Molten lead, astypical and illustrative of the heat transfer medium is introduced intothe top of the chamber 302 through inlet pipe 312 having a series oflaterally distributed nozzles 314 which rain the liquid metal downwardas a discontinuous phase dispersed in molten salt continuous phasethrough the upwardly moving column of molten salt. The gravitydifferential causes the lead to fall through the rising salt to coalescein a pool 316 in the lower reaches 318 of the chamber 302. The coalescedmolten lead displaces the molten salt upward and itself is drawn offthrough outlet pipe 320 and passed to the steam heat exchange step e.g.through line 68 to heat exchanger 70 (FIG. 2).

The molten salt moves upwardly through the heat exchanger chamber 302passing from a discontinuous phase in the liquid metal to a continuousphase in which the metal is discontinuous, and is drawn off throughoutlet pipe 322 e.g. to recycle through line 64 (FIG. 2). Theresubdivision and dispersion of the molten lead through the salt, or viceversa is carried out to a degree providing the most intimate form ofcontact for fastest heat transfer given an assumed height of chamber302. In a typical process the lead enters the chamber interior 310 at atemperature between 350° and 400° C. and a pressure between 10 and 50atmospheres. The lead in outlet pipe 320 is typically increased intemperature to about 900° C. and decreased in pressure by approximately2- 5 atmospheres. Conversely the molten salt, entering at temperaturesand pressures given just above, in outlet pipe 322 is at a temperatureabout 400° C. and a pressure about 10% below salt incoming pressure.

Consistent with the overall process approach of using heat mosteffectively, the chamber 302 is provided with surrounding jackets andinsulated as well. Thus wall 324, congruent with chamber wall 304 anddefining an inner annular space 326 therewith is provided. Relativelycool molten lead, e.g. at 350° C. is passed along the length of chamberwall 304 in inner annular space 326 upward from inlet 328 to the inletpipe 312 for dispersion into the chamber interior 310, accumulatingadditional heat in such passage and also protecting the supportstructures (not shown) of the chamber 302. Outward of inner annularspace a further congruent wall 330 is provided spaced from wall 324 anddefining therewith an outer annular space 332 which jackets the innerannular space 326 and the chamber 302. Steam or other process fluid maybe passed through the outer annular space 332 from inlet 334 to outlet336 absorbing heat indirectly emanated from the chamber 302 and throughthe lead in inner annular space 326, while further protecting thechamber support structure. Finally a support structure, shell 338 isprovided congruent with the chamber 302 and enclosing the walls 324 and330, spaced therefrom by an insulative layer 340.

HORIZONTAL HEAT EXCHANGER

The heat exchange between salt and lead may be effected in a horizontalheat exchanger shown at 342 in FIG. 9. Analogously to the reactor ofFIG. 4, described above, the heat exchanger 342 is discoid in form andjacketed. Thus the heat exchanger 342 comprises a wall 344 supportedcentrally by wall 346 defining an outlet passage 348 for steam beingheated indirectly by the apparatus, the wall 344 defining a heatexchange chamber 350 having a liquid metal e.g. molten lead inlet in theform of plural radially spaced apertures 351 just outward of the chambercenter line 352 and communicating the chamber interior 354 with a firstjacket space 356 supplied relatively cool molten lead through inlet 358.The lead is passed the length of the chamber wall 344 in advance ofinlet aperture 351 and once through the chamber 350 is collected atoutlet pipe 360 e.g. for passage to steam heat exchanger 70 through line68 (FIG. 2). The lead is introduced tangentially to flow in a spiralthrough the heat exchanger in the manner of the salt solution in thereactor of FIGS. 3 and 4. Similarly, molten salt is introducedtangentially into the chamber interior 354 through openings 362communicating annular plenum 364 leading from molten salt inlet 366 withthe chamber interior. The salt is passed spirally inward to outlet 368as the molten lead passes spirally outward, the two fluids beingseparated by centrifugal forces attending their spiraling movement,which tend to force the molten lead out and the molten salt in bydisplacement. As in the vertical embodiment the apparatus is jacketed bya wall 370 which defines a flow passage 372 for steam entering at inlet374 and exiting at 348 which combined with the lead in space 356protects the chamber 342 supports and heats process fluids at the sametime. Also as in the vertical embodiment, each fluid is introduced anddispersed in the other as the continuous phase and then coalesced fromits dispersion to form the continuous phase.

In practice both the vertical heat exchanger of FIG. 8 and the discoidembodiment of FIG. 9 contain in one portion a salt continuous phase anda discontinuous liquid metal phase, adjacent the point of introductionof the liquid metal into the salt; and a liquid metal continuous phaseand a salt discontinuous phase adjacent the point of introduction of themolten salt into the liquid metal. That is each fluid is introduced intothe other by spraying or otherwise to be dispersed, and in passagethrough the heat exchanger the dispersed fluid particles or dropletscoalesce and combine into a continuous phase. Thus the heat transfer ismaximized between the phases. The level of the interface region between(lower) continuous metal phase and (upper) continuous salt phase willvary in particular heat exchangers, determined by the extent ofdisplacement of the salt by the falling to the bottom of the heatexchanger.

STEAM HEAT EXCHANGE

The aforedescribed salt-lead heat exchangers may be used to like effectas the heat exchanger 70 (FIG. 2) with steam being the relatively lessdense fluid rather than salt. The lead if desired may be scavenged ofsalt traces prior to entering the heat exchanger 70 (FIG. 2) to avoidcontamination of the steam which is to be used to drive a turbinegenerator. In general, the molten lead supplied to the heat exchanger 70from a FIG. 8 or FIG. 9 heat exchanger will be at a temperature ofbetween 800° and 1000° C. and a pressure between about 40 to 200atmospheres. The steam entering the heat exchange will be between 150°and 250° C. in temperature and at the pressure of the leadapproximately. Exiting from the heat exchanger 70 will be lead atbetween 350° and 400° C. and 2-5 atmospheres lower pressure, and steamat about 10-200 atmospheres and between 650° and 800° C.

ORE SMELTING

As mentioned above, the source of oxygen for fuel reactant combustioncan be an ore, such as nickel or iron ore, with the smelting of the oreoccurring simultaneously with the combustion of the fuel reactant. Forthis purpose and with reference to FIG. 2 ore in finely comminuted formis introduced into the reactor 12 through line 13 to be intermixed withthe molten salt solution, in lieu of air from line 10. The reduction ofore proceeds and metal resulting is taken off at line 15; the combustiongases are separated through line 34, as in the air oxidizer embodiment.

FLUID SEALING

At various points in the process it will be desirable to have pumps andother apparatus which have impellers on rotating shafts in contact withthe high pressure fluid systems described herein. To protect shaftdriving motors and the general apparatus environment against leakagefrom the process vessels and to supplement and augment conventionalO-ring seals, there is provided an improved shaft seal shown in FIG. 10.With reference to FIG. 10 the apparatus chamber 400 is illustrative of apump housing or the like and includes a shaft 402 driven rotatably by amotor (not shown) in bearing 404. A packing gland 406 seals the shaft402. The packing gland 406 comprises a block 408 having a bore 410closely surrounding the shaft 402 and radially enlarged at 412 toaccommodate a first O-ring seal 414 which bears against the shaft insealing relation, and spaced axially therefrom in radial enlargement 413a second O-ring seal 416 which likewise bears against the shaft. Betweenthe O-rings 414 and 416 there is provided a passageway 418 through theblock 408 including an inlet portion 420, a pair of coaxial annularrecesses 422, 424, and an outlet portion 426. In operation, a fluidunder high pressure, e.g. not less than the fluid pressure with thechamber 400, and at a lower temperature, is forced through thepassageway 418 pressurizing the O-rings 414, 416. Leakage through theO-ring 414 is thus toward the chamber 400. The fluid in passageway 418is selected to be compatible with the particular fluid in the chamber400 and lower melting e.g. if the chamber fluid is molten lead, Wood'smetal may be used in the passageway; if the chamber fluid is moltensalt, a hydrate of that salt, which is lower melting, may be used in thepassageway. In this manner the seals 414, 416 may be fluid pressurizedwith a system-fluid compatible material, and while being protectedagainst the higher temperatures of the system fluids. That is the salthydrate being lower melting can be circulated through the passageway 418at a temperature well below that of its nonhydrated molten salt, and theheat exposure therefore of the O-ring seals 414, 416 is correspondinglyless and thus life correspondingly greater.

EXAMPLE

A molten salt system comprising mixed lithium, sodium, potassium andmagnesium chlorides and heated to a molten condition at between 375° and400° C. is blended with shearing with coal of the bituminous typesuitably prepulverized until solubilized into a single phase homogenate.

The dissolved coal is initially treated to drive off volatiles at 400°C. and 10 atmospheres. The molten salt solution of the coal residuals,typically low hydrogen polynucleated aromatics is passed to thecombustion reactor when the coal residual is burned, by passing air orother oxidizing gas differentially through the molten salt-fuel reactantoxidizing fuel and heating the molten salt to the range of 900-1000 C.The exhaust gases have their heat extracted through heat exchangers. Theheat content of the molten salt is extracted by a double cascade ofdirect contact (fluid commingling) heat exchangers which transfer theheat content from salt, to liquid metal, to steam to produce steam for asteam turbine with the steam being continuously recycled. The moltensalt having yielded its heat is recycled, again at about 375° to 400° tothe solubilization zone for recharging with fresh feedstock.

SUMMARY OF ADVANTAGES

The described process and apparatus provides a novel and highlyadvantageous system particularly for the combustion of coal, coalresidues and petroleum residues and for the transfer of heat in the mostrapid and efficient way, to steam, for the generation of power. Amongthe several outstanding benefits of the process and apparatus areminimal size, weight, and cost, limited requirement for imported powerto the process, maximal utilization of available energies through theprocess, and minimal loss of energy, i.e. heat, to the atmosphere, allwhile obtaining maximum heat from the feedstock, without air pollutionhazards.

I claim:
 1. In the process for the generation and recovery of heat fromhighly aromatic, refractory carbonaceous fuel reactants which includesoxidizing the fuel in a molten salt matrix within a reaction zone andrecovering heat of combustion from the salt matrix, dissolving the fuelin the salt to form a salt-fuel reactant solution, passing an oxidizinggas through said reactant solution to effect said oxidation, exhaustinghot combustion gases from said solution, expanding and cooling saidcombustion gases through an expansion motor, and compressing saidoxidizing gas with the energy of said expansion in advance of passingthe same through said reactant solution.
 2. The process according toclaim 1 in which said gas is free oxygen containing.
 3. The processaccording to claim 2 in which said gas is air.
 4. The process accordingto claim 2 including also preheating and compressing said oxidizing gasin advance of passage through said salt solution.
 5. The processaccording to claim 1 including also heat exchanging said hot combustiongases with said compressed oxidizing gas being passed to the salt-fuelsolution, in advance of expanding and cooling said hot combustion gases.6. The process according to claim 5 including also heat exchangingexpanded and cooled combustion gases with said compressed oxidizing gasprior to further heat exchange with hot combustion gases.
 7. Apparatusfor the generation and recovery of heat from highly aromatic, refractorycarbonaceous fuel reactants, said apparatus comprising a reactor, meansfor mixing said fuel reactants into molten salt to form a salt-fuelreactant solution, means for introducing said solution into the reactor,said reactor defining a through passage for the salt-fuel reactantsolution, means to pass a free oxygen-containing gas through saidreactor differentially to the salt-fuel reactant solution in combustionheat absorbing relation, means to pass exhaust gases from said reactor,means to expand and do work with said exhaust gases including thecompression and heating of said free-oxygen containing gas passed intothe reactor; means beyond said reactor to transfer said heat from saidsalt including a high specific heat fluid; and means to recharge saidmolten salt with fresh fuel reactant following heat transfer and toreturn said recharged salt to said reactor.
 8. Apparatus according toclaim 7 including also a turbo-expander and compressor and means to passexhaust gases through the expander and means to pass free oxygencontaining gas through the compressor, said expander being coupled tosaid compressor to compress said free oxygen containing gas with theexpansion energy of said exhaust gases.
 9. Apparatus according to claim8 including also means to pass said high specific heat fluid across theexternal surface of reactor to absorb heat emanated therefrom. 10.Apparatus according to claim 9 including also means to pass said oxygencontaining gas in indirect heat transfer relation with said fluid topreheat said gas for said reactor.
 11. Apparatus according to claim 10in which said reactor is generally cylindrical and provided with asalt-fuel solution inlet, and including also a first external jacketenclosing said reactor and a second external jacket enclosing said firstjacket; said first jacket defining a flow passage for said heat transferfluid; said second jacket communicating with said reactor interior anddefining a flow passage for said gas to said reactor interior. 12.Apparatus according to claim 11 in which said reactor terminates in asalt receiving receptacle having a salt outlet opposite the salt-fuelsolution inlet and including also gas inlets adjacently inward of saidreceptacle.
 13. Apparatus according to claim 7 including also means todisperse said salt-fuel solution into droplets moving differentiallypast said gas within said reactor.
 14. Apparatus according to claim 13in which said reactor is extended and said salt-fuel solution isintroduced at one terminus of said reactor, and including also meansintroducing said gas through an inlet at the opposed terminus of saidreactor.
 15. Apparatus according to claim 14 in which said reactor isvertically extended and said salt-fuel solution droplet-dispensing inletis located at the upper end of said reactor, and including also means topass said gas upward through said reactor at a rate suspending saiddroplets in dynamic equilibrium in a zone adjacent the gas inlet to saidreactor.
 16. Apparatus according to claim 15 in which said gas ispreheated indirectly by heat of combustion in advance of introductioninto said reactor.
 17. Apparatus according to claim 16 including alsomeans passing said heat transfer fluid between said reactor and said gasas an indirect heat transfer medium.
 18. Apparatus according to claim 14in which said reactor is discoid and said salt-fuel solution dropletdispensing inlet is located at the central portion of said reactor, andincluding also means to pass said gas inward through said reactor at arate and in a direction suspending said droplets in dynamic equilibriumin an annular zone adjacent the gas inlet to said reactor.
 19. Apparatusaccording to claim 18 in which said reactor further includes at itsperiphery a tangentially oriented gas inlet means and a gas outlet meansat the central portion thereof arranged to pass gas along a spiral pathinwardly through said reactor.
 20. Apparatus according to claim 19including opposed upper and lower salt-fuel solution inlet nozzlesangularly related to intersect streams of said solution for dispersionthereof within said reactor.
 21. Apparatus according to claim 19including also means to preheat gas to be introduced into said reactorwith heat emanated from said reactor.
 22. Apparatus according to claim19 in which said reactor includes external support structure andincluding also means to pass heat transfer fluid across the reactorexternal surface to absorb heat emanated from said reactor to protectsaid external support structure.
 23. Apparatus according to claim 22including also means to transfer heat indirectly from said heat transferfluid to said gas to be introduced into said reactor to preheat saidgas.
 24. Apparatus according to claim 23 including also a first jacketgenerally enclosing said discoid reactor, a second jacket generallyenclosing said first jacket, said first jacket defining a passage forsaid heat transfer fluid in heat transfer relation with said reactor;said second jacket defining a through passage in heat transfer relationto said first passage for gas to be introduced into said reactor; andincluding also a gas inlet port communicating said gas passage jacketwith the reactor interior in fluid free relation through said firstjacket and radially inward of said salt collector.
 25. Apparatusaccording to claim 8 including also means to heat exchange said exhaustgases before and after their expansion with compressed free oxygencontaining gas.
 26. In the process for the generation and recovery ofheat from highly aromatic, refractory carbonaceous fuel reactants whichincludes oxidizing the fuel in a molten salt matrix within a reactionzone and recovering heat of combustion from the salt matrix, circulatingsaid molten salt to and from said reaction zone to bring fresh chargesof fuel reactant into the zone and heat out of the zone in a reactionstream loop, dissolving the fuel charges in the salt to form a salt-fuelreactant solution in said loop for reactant oxidation in said zone,circulating metallic liquid sequentially through said salt indifferential flow relation to heat exchange said metallic liquid withsaid salt, through steam to transfer exchanged heat of combustionthereto, and back through said salt solution in a heat transfer loop,and circulating said heated steam to a steam energy consuming loop torecover heat and back in a steam loop to said heat transfer loop forregeneration of heated steam.
 27. The process according to claim 26 inwhich the fuel reactant is subanthracite coal and including alsopreheating said fuel reactant in the molten salt in advance of thereaction zone to substantially free the reactant of components volatileat 400° C. and 10 atmospheres.
 28. The process according to claim 26including also passing said metallic liquid in heat exchange relationover the exterior surfaces of the reaction zone.
 29. The processaccording to claim 19 including also passing said metallic liquid inindirect heat exchange relation over the exterior surfaces of thereaction zone.
 30. The process according to claim 26 including alsopassing said salt and metallic liquid countercurrently along an extendedheat exchange path and differentially at opposite ends of said path tomaintain relatively longer contact of the metallic liquid with the saltat maximum temperature and relatively shorter contact thereof withminimum temperature salt along the path.
 31. The process according toclaim 30 in which said metallic liquid is dispersed throughout said saltin a multiplicity of different mass droplets, and including alsosubjecting said droplets to opposing forces along said path, one ofwhich forces is proportional to the specific mass of said droplets, andsegregating said droplets by their specific mass for separation of thegreater mass droplets selectively.
 32. The process according to claim 26in which said metallic liquid is lead and including also alternatelydispersing said lead into droplets in the salt for reception of heat andcoalescing for separation from the salt.
 33. The process according toclaim 32 in which differential flow of salt and the lead dropletstherein is maintained by balancing forces acting on said lead in amanner relatively increasing the lead exposure to maximum temperaturesalt and relatively decreasing the lead exposure to minimum temperaturesalt and responsive to the mass of the droplets so that upon coalescenceof the droplets they are separable from the salt.
 34. The processaccording to claim 33 including also passing said liquid lead over theexterior surfaces of the reaction zone to retain heat normally emanatedfrom said zone in the process.
 35. The process according to claim 34including also passing a free oxygen containing gas in indirect heatexchange with the liquid lead at the exterior surface of the reactionzone, and passing said gas through preheat into the reaction zone tooxidize the fuel reactant therein.
 36. The process according to claim 35in which the reaction zone is vertically extended and including alsowithin the reaction zone raining molten salt-fuel reactant solution indroplet form through an updraft of air as the oxidizing gas, andcollecting molten salt containing the heat of combustion at the lowerreaches of the reaction zone.
 37. The process according to claim 36including also balancing the gravitational forces acting on the fallingmolten salt-fuel reactant solution droplets with the force of air tosuspend temporarily the droplets above the lower reaches of the reactionzone for a time to substantially free the salt of fuel reactant.
 38. Theprocess according to claim 35 in which the reaction zone is discoid andincluding also introducing said molten salt-fuel reactant centrallythereof for outward passage through the reaction zone in droplet form,introducing air tangentially at the periphery of said reaction zonealong a spiral path extending toward the center of said zone in a mannerentraining said salt solution-fuel reactant droplets for passage towardthe center of said zone, and simultaneously subjecting said droplets tocentrifugal forces opposing such passage, and collecting molten saltcontaining heat of combustion at the peripheral reaches of said reactionzone.
 39. The process according to claim 38 including also balancing thecentrifugal forces acting on the molten salt-fuel reactant solutiondroplets with the force of air to suspend temporarily the dropletsinwardly of the reaction zone periphery for a time to substantially freethe salt of fuel reactant.
 40. Apparatus for the generation and recoveryof heat from highly aromatic, refractory carbonaceous fuel reactants;said apparatus comprising a reactor, means for mixing said fuelreactants into molten salt to form a salt-fuel reactant solution, meansfor introducing said solution into the reactor, said reactor defining athrough passage for the salt-fuel reactant solution, means to pass afree oxygen-containing gas through said reactor differentially to thesalt fuel reactant solution in combustion heat absorbing relation, meansto pass exhaust gases from said reactor, means to recharge said moltensalt with fresh fuel reactant following heat transfer and to return saidrecharged salt to said reactor and means beyond said reactor to transfersaid heat from said salt comprising a first heat exchanger, a secondheat exchanger, and loop means passing a high specific heat fluid mediumthrough said first heat exchanger with said salt in heat transferringrelation, and through said second heat exchanger with steam, to transferthe salt heat to said steam through said fluid medium; and steam turbinemeans adapted to receive steam from said second heat exchanger. 41.Apparatus according to claim 40 in which said high specific heat fluidcomprises a metallic liquid and including also means to pass said liquidinto and out of heat exchange contact with salt in said heat exchanger,and second heat exchange means to transfer heat from said metallicliquid steam.
 42. Apparatus according to claim 41 in which said firstheat exchanger is a direct contact heat exchanger.
 43. Apparatusaccording to claim 41 in which said second heat exchanger is a directcontact heat exchanger.
 44. Apparatus according to claim 43 in whichsaid first heat exchanger is a direct contact heat exchanger. 45.Apparatus according to claim 44 in which said first heat exchangercomprises an extended exchange chamber and means to pass said salt andsaid metallic liquid differentially through said exchange chamber. 46.Apparatus according to claim 45 in which said first heat exchangercomprises a vertically elongated exchange chamber having a metallicliquid inlet at the upper portion thereof and a metallic liquid outletat the lower portion thereof, said chamber further having a salt inletat the lower portion thereof and a salt outlet at the upper portionthereof for passage of salt upwardly through the chamber, and means atthe metallic liquid inlet to disperse the liquid into and through theupward moving salt and at the liquid outlet to recover said liquid,coalesced and with the transferred heat of said salt.
 47. Apparatusaccording to claim 46 in which the metallic liquid is molten lead. 48.Apparatus according to claim 45 in which said second heat exchangercomprises means to intimately interdisperse said metallic liquid andsteam to transfer said salt heat contained by said liquid thereby tosaid steam.
 49. Apparatus according to claim 47 in which said secondheat exchanger comprises means to intimately interdisperse said lead andsteam to transfer said salt heat contained in said lead thereby to saidsteam.
 50. Apparatus according to claim 40 including also means torecycle steam from the steam turbine to the second heat exchanger forreheating.
 51. Apparatus according to claim 45 in which said first heatexchanger includes external support structure and including also meansto pass relatively cooler heat transferring metallic liquid over theexternal surface of said first heat exchanger to absorb heat radiatedfrom said heat exchange to protect the external support structurethereof.
 52. Apparatus according to claim 51 including a first jacketgenerally enclosing said first heat exchange means, said jacket defininga flow passage for said metallic liquid.
 53. Apparatus according toclaim 52 including also means to pass process steam in heat transferringrelation across the external surface of said first heat exchanger. 54.Apparatus according to claim 53 including a second jacket generallyenclosing said first jacket and defining a passage for process steam inheat transfer relation with the metallic liquid in said first jacket.